<PAGE>   1

                                                   Registration No. 333-________
                                                            Filed April 13, 1998

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549



                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933


                     Peoples Heritage Financial Group, Inc.
    (Exact Name of Registrant as specified in its Articles of Incorporation)

        Maine                                              01-0437984
(State of incorporation)                       (IRS Employer Identification No.)

                                  P.O. Box 9540
                               One Portland Square
                           Portland, Maine 04112-9540


          (Address of principal executive offices, including zip code)


   Options to purchase Common Stock of the Registrant issued by the Registrant
   pursuant to an Agreement and Plan of Merger, dated as of October 27, 1997,
     between the Registrant and CFX Corporation ("CFX"), upon conversion of
    outstanding options to purchase Common Stock of CFX issued by CFX under
         its 1997 Long-Term Incentive Plan, its 1995 Stock Option Plan,
          its 1986 Stock Option Plan, the Safety Fund Corporation 1994
  Incentive and Nonqualified Stock Option Plan, the Community Bankshares, Inc.
    1992 Stock Option Plan, the Concord Savings Bank 1988 Stock Option Plan
    and the Portsmouth Bank Shares, Inc. Revised 1987 Stock Option and Stock
                            Appreciation Rights Plan


                           (Full Titles of the Plans)
<TABLE>
<S>                                                 <C>
William J. Ryan                                     Copies to:
Chairman, President and                             Gerard L. Hawkins, Esq.
  Chief Executive Officer                           Elias, Matz, Tiernan & Herrick L.L.P.
Peoples Heritage Financial Group, Inc.              734 15th Street, N.W.
P.O. Box 9540                                       Washington, D.C.  20005
One Portland Square                                 (202) 347-0300
Portland, Maine 04112-9540
(207) 761-8500
(Name, address and telephone number of
agent for service)
</TABLE>

                           Page 1 of 15 pages Index to
                         Exhibits is located on page 5.
<PAGE>   2
                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>

        Title of
       Securities         Amount         Proposed Maximum          Proposed Maximum            Amount of
          to be            to be          Offering Price               Aggregate              Registration
       Registered      Registered(1)       Per Share(3)            Offering Price(3)              Fee
-----------------------------------------------------------------------------------------------------------
<S>                    <C>                   <C>                    <C>                       <C>
Common Stock,
 par value $.01        380,672(2)            $21.995                $ 8,372,881               $2,470.00
</TABLE>





(1) Together with an indeterminate number of additional shares which may be
necessary to adjust the number of shares of common stock, par value $.01 per
share ("Common Stock"), of Peoples Heritage Financial Group, Inc. (the "Company"
or "Registrant") registered hereby as a result of a stock split, stock dividend
or similar adjustment of the outstanding Common Stock.

(2) Represents the number of shares of Common Stock of the Company reserved for
issuance as a result of the conversion of options to purchase common stock of
CFX Corporation ("CFX") into options to purchase Common Stock of the Company
pursuant to an Agreement and Plan of Merger, dated as of October 27, 1997,
between the Company and CFX.

(3) Estimated solely for the purpose of calculating the registration fee, which
has been calculated pursuant to Rule 457(h) promulgated under the Securities Act
of 1933, as amended ("Securities Act"). The Proposed Maximum Offering Price Per
Share is equal to the weighted average exercise price for the options, as
converted, to purchase shares of Common Stock.


         This Registration Statement shall become effective automatically upon
the date of filing in accordance with Section 8(a) of the Securities Act and 17
C.F.R. Section 230.462.

                                        2
<PAGE>   3
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.     INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents filed or to be filed with the Securities and
Exchange Commission (the "Commission") are incorporated by reference in this
Registration Statement:

                 (a) The Company's Annual Report on Form 10-K for the year ended
         December 31, 1997.

                 (b) All reports filed by the Company pursuant to Section 13(a)
         or 15(d) of the Securities Exchange Act of 1934, as amended ("Exchange
         Act"), since the end of the fiscal year covered by the Form 10-K
         referred to in clause (a) above.

                 (c) The description of the Common Stock of the Company
         contained in the Company's Registration Statement on Form S-4 (File No.
         333-43551) filed on December 31, 1997.

                 (d) All documents filed by the Company pursuant to Sections
         13(a), 13(c), 14 or 15(d) of the Exchange Act after the date hereof and
         prior to the filing of a post-effective amendment which indicates that
         all securities offered have been sold or which deregisters all
         securities then remaining unsold.

         Any statement contained in this Registration Statement, or in a
document incorporated or deemed to be incorporated by reference herein, shall be
deemed to be modified or superseded for purposes of this Registration Statement
to the extent that a statement contained herein, or in any other subsequently
filed document which also is or is deemed to be incorporated by reference
herein, modifies or supersedes such statement. Any such statement so modified or
superseded shall not be deemed, except as so modified or superseded, to
constitute a part of this Registration Statement.

ITEM 4.     DESCRIPTION OF SECURITIES.

         Not applicable because the Common Stock is registered under Section 12
of the Exchange Act.

ITEM. 5.    INTERESTS OF NAMED EXPERTS AND COUNSEL.

         Not applicable.


                                        3
<PAGE>   4
ITEM 6.     INDEMNIFICATION OF DIRECTORS AND OFFICERS.


         Section 719 of the MBCA sets forth certain circumstances under which
directors, officers, employees and agents may be indemnified against liability
which they may incur in their capacity as such. Indemnification may be provided
against expenses, including attorneys' fees, judgments, fines and amounts paid
in settlement actually and reasonably incurred; provided that no indemnification
may be provided with respect to any matter where such person shall have been
finally adjudicated (i) not to have acted honestly or in the reasonable belief
that such action was in or not opposed to the best interests of the corporation
or its shareholders, or (ii) with respect to any criminal action, to have had
reasonable cause to believe such conduct was unlawful. A corporation may not
indemnify a person with respect to any action or matter by or in the right of
the corporation as to which that person is finally adjudicated to be liable to
the corporation unless the court in which the action was brought determines
that, in view of all the circumstances, that person is fairly and reasonably
entitled to indemnity for such amounts as the court deems reasonable. To the
extent such person has been successful on the merits or otherwise in defense of
such action, that person shall be entitled to indemnification. Any
indemnification, unless ordered by a court or required in the corporation's
bylaws, shall be made only as authorized in the specific case upon a
determination by the board of directors that indemnification is proper in the
circumstances and in the best interests of the corporation. Expenses incurred in
defending an action may be paid by the corporation in advance of the final
disposition of that action upon a determination made that the person seeking
indemnification satisfied the standard of conduct required for indemnification
and receipt by the corporation of a written undertaking by or on behalf of such
person to repay that amount if that person is finally adjudicated to not have
met such standard or not be entitled to such indemnification. In addition,
Section 719 of the MBCA provides that a corporation may purchase and maintain
insurance on behalf of directors, officers, employees and agents against
liability whether or not the corporation would have the power to indemnify such
person against liability under such section. See Title 13-A Maine Revised
Statutes Annotated Section 719.

         Article VI of the Bylaws of the Company provides that the directors,
officers, employees and agents of the Company shall be indemnified to the full
extent permitted by the MBCA. Such indemnity shall extend to expenses, including
attorney's fees, judgments, fines and amounts paid in the settlement,
prosecution or defense of the foregoing actions. Directors and officers also may
be indemnified pursuant to the terms of various employee benefit plans of the
Company. In addition, the Company carries a liability insurance policy for its
directors and officers.

ITEM 7.     EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable because no restricted securities will be reoffered or
resold pursuant to this Registration Statement.

                                        4
<PAGE>   5
ITEM 8.     EXHIBITS


         The following exhibits are filed with or incorporated by reference into
this Registration Statement on Form S-8 (numbering corresponds to Exhibit Table
in Item 601 of Regulation S-K):

<TABLE>
<CAPTION>
         No.           Exhibit                                                                   Page
         ---           -------                                                                   ----
<S>      <C>           <C>                                                                       <C>
         4             Common Stock Certificate                                                  (1)

         5             Opinion of Elias, Matz, Tiernan & Herrick L.L.P.
                        as to the legality of the securities                                     E-1

         23.1          Consent of Elias, Matz, Tiernan & Herrick L.L.P.
                        (contained in the opinion included as Exhibit 5)                         --

         23.2          Consent of KPMG Peat Marwick LLP.                                         E-3

         23.3          Consent of Wolf & Company, P.C.                                           E-4

         23.4          Consent of Shatswell, MacLeod & Company, P.C.                             E-5

         24             Power of attorney for any subsequent amendments (located
                        in the signature pages of this
                        Registration Statement).                                                 --

         99.1          CFX Corporation 1997 Long-Term Incentive
                        Plan                                                                     (2)

         99.2          CFX Corporation 1995 Stock Option Plan                                    (3)

         99.3          CFX Corporation 1986 Stock Option Plan                                    (4)

         99.4          Safety Fund Corporation 1994 Incentive and
                        Nonqualified Stock Option Plan                                           (5)

         99.5          Community Bankshares, Inc. 1992 Stock Option Plan                         (6)

         99.6          Concord Savings Bank 1988 Stock Option Plan                               (6)

         99.7          Portsmouth Bank Shares, Inc. Revised 1987
                        Stock Option and Stock Appreciation Rights
                        Plan                                                                     (7)
</TABLE>




                                        5
<PAGE>   6
      (1)   Incorporated by reference from the Company's Registration Statement
            on Form 8-B, filed with the Commission on May 20, 1988.

      (2)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by CFX Corporation with the Commission on December 27,
            1997 (Commission File No. 333-43255).

      (3)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by CFX Corporation with the Commission on August 14, 1995
            (Commission File No. 33-61787).

      (4)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by CFX Corporation with the Commission on September 8,
            1987 (Commission File No. 33-17071).

      (5)   Incorporated by reference from the Annual Report on Form 10-KSB for
            the year ended December 31, 1994 filed by The Safety Fund
            Corporation with the Commission on March 31, 1995 (Commission File
            No. 2-50084).

      (6)   Incorporated by reference from the Post-Effective No. 1 on Form S-8
            to the Registration Statement on Form S-4 filed by CFX Corporation
            with the Commission on September 23, 1997 (Commission File No.
            333-29229).

      (7)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by Portsmouth Bank Shares, Inc. with the Commission on
            August 29, 1988 (Commission File No. 33-24050).

ITEM 9.     UNDERTAKINGS.

     The undersigned Registrant hereby undertakes:

     1.     To file, during any period in which offers or sales are being
made, a post-effective amendment to this Registration Statement (i) to include
any prospectus required by Section 10(a)(3) of the Securities Act of 1933, (ii)
to reflect in the prospectus any facts or events arising after the effective
date of the Registration Statement (or the most recent post-effective amendment
thereof) which, individually or in the aggregate, represent a fundamental change
in the information set forth in the Registration Statement, and (iii) to include
any material information with respect to the plan of distribution not previously
disclosed in the Registration Statement or any material change in such
information in the Registration Statement; provided, however, that clauses (i)
and (ii) do not apply if the information required to be included in a
post-effective amendment by those clauses is

                                        6
<PAGE>   7
contained in periodic reports filed by the Registrant pursuant to Section 13 or
Section 15(d) of the Exchange Act that are incorporated by reference in the
Registration Statement.

      2.    That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

      3.    To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

      4.    That, for the purposes of determining any liability under the
Securities Act of 1933, each filing of the Registrant's annual report pursuant
to Section 13(a) or Section 15(d) of the Exchange Act that is incorporated by
reference in the Registration Statement shall be deemed to be a new registration
statement relating to the securities offered therein, and the offering of such
securities at that time shall be deemed to be the initial bona fide offering
thereof.

      5.    Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions or otherwise, the
Registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act of
1933 and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act of 1933 and will be governed by the final adjudication of such issue.

                                        7
<PAGE>   8
                                   SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Portland, State of Maine, on this 13th day of April
1998.

                                    PEOPLES HERITAGE FINANCIAL
                                      GROUP, INC.


                                    By:/s/ William J. Ryan
                                       ------------------------------------
                                       William J. Ryan, Chairman, President
                                       and Chief Executive Officer


      Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated. Each person whose signature appears below
hereby makes, constitutes and appoints William J. Ryan his or her true and
lawful attorney, with full power to sign for such person and in such person's
name and capacity indicated below, and with full power of substitution any and
all amendments to this Registration Statement, hereby ratifying and confirming
such person's signature as it may be signed by said attorney to any and all
amendments.


/s/ Robert P. Bahre                                 April 13, 1998
------------------------------------------
Robert P. Bahre
Director


/s/ Everett W. Gray                                 April 13, 1998
------------------------------------------
Everett W. Gray
Director


/s/ Andrew W. Greene                                April 13, 1998
------------------------------------------
Andrew W. Greene
Director


/s/ Katherine M. Greenleaf                          April 13, 1998
------------------------------------------
Katherine M. Greenleaf
Director

                                        8
<PAGE>   9
/s/ Dana Levensen                                   April 13, 1998
------------------------------------------
Dana Levensen
Director


/s/ Robert A. Marden, Sr.                           April 13, 1998
------------------------------------------
Robert A. Marden, Sr.
Director


/s/ Malcolm W. Philbrook, Jr.                       April 13, 1998
------------------------------------------
Malcolm W. Philbrook, Jr.
Director


/s/ Pamela Plumb                                    April 13, 1998
------------------------------------------
Pamela Plumb
Director


/s/ William J. Ryan                                 April 13, 1998
------------------------------------------
William J. Ryan
Chairman, President and Chief
  Executive Officer
(principal executive officer)


/s/ Curtis M. Scribner                              April 13, 1998
------------------------------------------
Curtis M. Scribner
Director


/s/ Paul R. Shea                                    April 13, 1998
------------------------------------------
Paul R. Shea
Director


/s/Davis P. Thurber                                 April 13, 1998
------------------------------------------
Davis P. Thurber
Director


/s/John E. Veasey                                   April 13, 1998
------------------------------------------
John E. Veasey
Director

/s/ Peter J. Verrill                                April 13, 1998
------------------------------------------
Peter J. Verrill
Executive Vice President, Chief
  Financial Officer and Treasurer
 (principal financial and accounting officer)
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1

                                                   Registration No. 333-________
                                                            Filed April 13, 1998

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                     Peoples Heritage Financial Group, Inc.
    (Exact Name of Registrant as specified in its Articles of Incorporation)

        Maine                                              01-0437984
(State of incorporation)                       (IRS Employer Identification No.)

                                  P.O. Box 9540
                               One Portland Square
                           Portland, Maine 04112-9540

          (Address of principal executive offices, including zip code)

   Options to purchase Common Stock of the Registrant issued by the Registrant
   pursuant to an Agreement and Plan of Merger, dated as of October 27, 1997,
     between the Registrant and CFX Corporation ("CFX"), upon conversion of
    outstanding options to purchase Common Stock of CFX issued by CFX under
         its 1997 Long-Term Incentive Plan, its 1995 Stock Option Plan,
          its 1986 Stock Option Plan, the Safety Fund Corporation 1994
  Incentive and Nonqualified Stock Option Plan, the Community Bankshares, Inc.
    1992 Stock Option Plan, the Concord Savings Bank 1988 Stock Option Plan
    and the Portsmouth Bank Shares, Inc. Revised 1987 Stock Option and Stock
                            Appreciation Rights Plan

                           (Full Titles of the Plans)
William J. Ryan                                     Copies to:
Chairman, President and                             Gerard L. Hawkins, Esq.
  Chief Executive Officer                           Elias, Matz, Tiernan & Herrick L.L.P.
Peoples Heritage Financial Group, Inc.              734 15th Street, N.W.
P.O. Box 9540                                       Washington, D.C.  20005
One Portland Square                                 (202) 347-0300
Portland, Maine 04112-9540
(207) 761-8500
(Name, address and telephone number of
agent for service)
Page 1 of 15 pages Index to
                         Exhibits is located on page 5.
2
                         CALCULATION OF REGISTRATION FEE
Title of
       Securities         Amount         Proposed Maximum          Proposed Maximum            Amount of
          to be            to be          Offering Price               Aggregate              Registration
       Registered      Registered(1)       Per Share(3)            Offering Price(3)              Fee
-----------------------------------------------------------------------------------------------------------
Common Stock,
 par value $.01        380,672(2)            $21.995                $ 8,372,881               $2,470.00
(1) Together with an indeterminate number of additional shares which may be
necessary to adjust the number of shares of common stock, par value $.01 per
share ("Common Stock"), of Peoples Heritage Financial Group, Inc. (the "Company"
or "Registrant") registered hereby as a result of a stock split, stock dividend
or similar adjustment of the outstanding Common Stock.

(2) Represents the number of shares of Common Stock of the Company reserved for
issuance as a result of the conversion of options to purchase common stock of
CFX Corporation ("CFX") into options to purchase Common Stock of the Company
pursuant to an Agreement and Plan of Merger, dated as of October 27, 1997,
between the Company and CFX.

(3) Estimated solely for the purpose of calculating the registration fee, which
has been calculated pursuant to Rule 457(h) promulgated under the Securities Act
of 1933, as amended ("Securities Act"). The Proposed Maximum Offering Price Per
Share is equal to the weighted average exercise price for the options, as
converted, to purchase shares of Common Stock.

         This Registration Statement shall become effective automatically upon
the date of filing in accordance with Section 8(a) of the Securities Act and 17
C.F.R. Section 230.462.

                                        2
3
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.     INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents filed or to be filed with the Securities and
Exchange Commission (the "Commission") are incorporated by reference in this
Registration Statement:

                 (a) The Company's Annual Report on Form 10-K for the year ended
         December 31, 1997.

                 (b) All reports filed by the Company pursuant to Section 13(a)
         or 15(d) of the Securities Exchange Act of 1934, as amended ("Exchange
         Act"), since the end of the fiscal year covered by the Form 10-K
         referred to in clause (a) above.

                 (c) The description of the Common Stock of the Company
         contained in the Company's Registration Statement on Form S-4 (File No.
         333-43551) filed on December 31, 1997.

                 (d) All documents filed by the Company pursuant to Sections
         13(a), 13(c), 14 or 15(d) of the Exchange Act after the date hereof and
         prior to the filing of a post-effective amendment which indicates that
         all securities offered have been sold or which deregisters all
         securities then remaining unsold.

         Any statement contained in this Registration Statement, or in a
document incorporated or deemed to be incorporated by reference herein, shall be
deemed to be modified or superseded for purposes of this Registration Statement
to the extent that a statement contained herein, or in any other subsequently
filed document which also is or is deemed to be incorporated by reference
herein, modifies or supersedes such statement. Any such statement so modified or
superseded shall not be deemed, except as so modified or superseded, to
constitute a part of this Registration Statement.

ITEM 4.     DESCRIPTION OF SECURITIES.

         Not applicable because the Common Stock is registered under Section 12
of the Exchange Act.

ITEM. 5.    INTERESTS OF NAMED EXPERTS AND COUNSEL.

         Not applicable.

                                        3
4
ITEM 6.     INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Section 719 of the MBCA sets forth certain circumstances under which
directors, officers, employees and agents may be indemnified against liability
which they may incur in their capacity as such. Indemnification may be provided
against expenses, including attorneys' fees, judgments, fines and amounts paid
in settlement actually and reasonably incurred; provided that no indemnification
may be provided with respect to any matter where such person shall have been
finally adjudicated (i) not to have acted honestly or in the reasonable belief
that such action was in or not opposed to the best interests of the corporation
or its shareholders, or (ii) with respect to any criminal action, to have had
reasonable cause to believe such conduct was unlawful. A corporation may not
indemnify a person with respect to any action or matter by or in the right of
the corporation as to which that person is finally adjudicated to be liable to
the corporation unless the court in which the action was brought determines
that, in view of all the circumstances, that person is fairly and reasonably
entitled to indemnity for such amounts as the court deems reasonable. To the
extent such person has been successful on the merits or otherwise in defense of
such action, that person shall be entitled to indemnification. Any
indemnification, unless ordered by a court or required in the corporation's
bylaws, shall be made only as authorized in the specific case upon a
determination by the board of directors that indemnification is proper in the
circumstances and in the best interests of the corporation. Expenses incurred in
defending an action may be paid by the corporation in advance of the final
disposition of that action upon a determination made that the person seeking
indemnification satisfied the standard of conduct required for indemnification
and receipt by the corporation of a written undertaking by or on behalf of such
person to repay that amount if that person is finally adjudicated to not have
met such standard or not be entitled to such indemnification. In addition,
Section 719 of the MBCA provides that a corporation may purchase and maintain
insurance on behalf of directors, officers, employees and agents against
liability whether or not the corporation would have the power to indemnify such
person against liability under such section. See Title 13-A Maine Revised
Statutes Annotated Section 719.

         Article VI of the Bylaws of the Company provides that the directors,
officers, employees and agents of the Company shall be indemnified to the full
extent permitted by the MBCA. Such indemnity shall extend to expenses, including
attorney's fees, judgments, fines and amounts paid in the settlement,
prosecution or defense of the foregoing actions. Directors and officers also may
be indemnified pursuant to the terms of various employee benefit plans of the
Company. In addition, the Company carries a liability insurance policy for its
directors and officers.

ITEM 7.     EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable because no restricted securities will be reoffered or
resold pursuant to this Registration Statement.

                                        4
5
ITEM 8.     EXHIBITS

         The following exhibits are filed with or incorporated by reference into
this Registration Statement on Form S-8 (numbering corresponds to Exhibit Table
in Item 601 of Regulation S-K):
No.           Exhibit                                                                   Page
         ---           -------                                                                   ----
4             Common Stock Certificate                                                  (1)

         5             Opinion of Elias, Matz, Tiernan & Herrick L.L.P.
                        as to the legality of the securities                                     E-1

         23.1          Consent of Elias, Matz, Tiernan & Herrick L.L.P.
                        (contained in the opinion included as Exhibit 5)                         --

         23.2          Consent of KPMG Peat Marwick LLP.                                         E-3

         23.3          Consent of Wolf & Company, P.C.                                           E-4

         23.4          Consent of Shatswell, MacLeod & Company, P.C.                             E-5

         24             Power of attorney for any subsequent amendments (located
                        in the signature pages of this
                        Registration Statement).                                                 --

         99.1          CFX Corporation 1997 Long-Term Incentive
                        Plan                                                                     (2)

         99.2          CFX Corporation 1995 Stock Option Plan                                    (3)

         99.3          CFX Corporation 1986 Stock Option Plan                                    (4)

         99.4          Safety Fund Corporation 1994 Incentive and
                        Nonqualified Stock Option Plan                                           (5)

         99.5          Community Bankshares, Inc. 1992 Stock Option Plan                         (6)

         99.6          Concord Savings Bank 1988 Stock Option Plan                               (6)

         99.7          Portsmouth Bank Shares, Inc. Revised 1987
                        Stock Option and Stock Appreciation Rights
                        Plan                                                                     (7)
5
6
      (1)   Incorporated by reference from the Company's Registration Statement
            on Form 8-B, filed with the Commission on May 20, 1988.

      (2)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by CFX Corporation with the Commission on December 27,
            1997 (Commission File No. 333-43255).

      (3)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by CFX Corporation with the Commission on August 14, 1995
            (Commission File No. 33-61787).

      (4)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by CFX Corporation with the Commission on September 8,
            1987 (Commission File No. 33-17071).

      (5)   Incorporated by reference from the Annual Report on Form 10-KSB for
            the year ended December 31, 1994 filed by The Safety Fund
            Corporation with the Commission on March 31, 1995 (Commission File
            No. 2-50084).

      (6)   Incorporated by reference from the Post-Effective No. 1 on Form S-8
            to the Registration Statement on Form S-4 filed by CFX Corporation
            with the Commission on September 23, 1997 (Commission File No.
            333-29229).

      (7)   Incorporated by reference from the Registration Statement on Form
            S-8 filed by Portsmouth Bank Shares, Inc. with the Commission on
            August 29, 1988 (Commission File No. 33-24050).

ITEM 9.     UNDERTAKINGS.

     The undersigned Registrant hereby undertakes:

     1.     To file, during any period in which offers or sales are being
made, a post-effective amendment to this Registration Statement (i) to include
any prospectus required by Section 10(a)(3) of the Securities Act of 1933, (ii)
to reflect in the prospectus any facts or events arising after the effective
date of the Registration Statement (or the most recent post-effective amendment
thereof) which, individually or in the aggregate, represent a fundamental change
in the information set forth in the Registration Statement, and (iii) to include
any material information with respect to the plan of distribution not previously
disclosed in the Registration Statement or any material change in such
information in the Registration Statement; provided, however, that clauses (i)
and (ii) do not apply if the information required to be included in a
post-effective amendment by those clauses is

                                        6
7
contained in periodic reports filed by the Registrant pursuant to Section 13 or
Section 15(d) of the Exchange Act that are incorporated by reference in the
Registration Statement.

      2.    That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

      3.    To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

      4.    That, for the purposes of determining any liability under the
Securities Act of 1933, each filing of the Registrant's annual report pursuant
to Section 13(a) or Section 15(d) of the Exchange Act that is incorporated by
reference in the Registration Statement shall be deemed to be a new registration
statement relating to the securities offered therein, and the offering of such
securities at that time shall be deemed to be the initial bona fide offering
thereof.

      5.    Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions or otherwise, the
Registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act of
1933 and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act of 1933 and will be governed by the final adjudication of such issue.

                                        7
8
                                   SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Portland, State of Maine, on this 13th day of April
1998.

                                    PEOPLES HERITAGE FINANCIAL
                                      GROUP, INC.

                                    By:/s/ William J. Ryan
                                       ------------------------------------
                                       William J. Ryan, Chairman, President
                                       and Chief Executive Officer

      Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated. Each person whose signature appears below
hereby makes, constitutes and appoints William J. Ryan his or her true and
lawful attorney, with full power to sign for such person and in such person's
name and capacity indicated below, and with full power of substitution any and
all amendments to this Registration Statement, hereby ratifying and confirming
such person's signature as it may be signed by said attorney to any and all
amendments.

/s/ Robert P. Bahre                                 April 13, 1998
------------------------------------------
Robert P. Bahre
Director

/s/ Everett W. Gray                                 April 13, 1998
------------------------------------------
Everett W. Gray
Director

/s/ Andrew W. Greene                                April 13, 1998
------------------------------------------
Andrew W. Greene
Director

/s/ Katherine M. Greenleaf                          April 13, 1998
------------------------------------------
Katherine M. Greenleaf
Director

                                        8
9
/s/ Dana Levensen                                   April 13, 1998
------------------------------------------
Dana Levensen
Director

/s/ Robert A. Marden, Sr.                           April 13, 1998
------------------------------------------
Robert A. Marden, Sr.
Director

/s/ Malcolm W. Philbrook, Jr.                       April 13, 1998
------------------------------------------
Malcolm W. Philbrook, Jr.
Director

/s/ Pamela Plumb                                    April 13, 1998
------------------------------------------
Pamela Plumb
Director

/s/ William J. Ryan                                 April 13, 1998
------------------------------------------
William J. Ryan
Chairman, President and Chief
  Executive Officer
(principal executive officer)

/s/ Curtis M. Scribner                              April 13, 1998
------------------------------------------
Curtis M. Scribner
Director

/s/ Paul R. Shea                                    April 13, 1998
------------------------------------------
Paul R. Shea
Director

/s/Davis P. Thurber                                 April 13, 1998
------------------------------------------
Davis P. Thurber
Director

/s/John E. Veasey                                   April 13, 1998
------------------------------------------
John E. Veasey
Director

/s/ Peter J. Verrill                                April 13, 1998
------------------------------------------
Peter J. Verrill
Executive Vice President, Chief
  Financial Officer and Treasurer
 (principal financial and accounting officer)