<PAGE>   1



                                                           Registration No. 333-
                                                           Filed January 4, 1999

                       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 July 20, 1998, as
 amended, between the Registrant and SIS Bancorp, Inc. ("SIS"), upon conversion
 of outstanding options to purchase Common Stock of SIS issued by SIS under its
        Director Stock Option Plan and its Management Stock Option 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>   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 Fee
   Registered         Registered(1)        Per Share(3)      Offering Price(3)
----------------------------------------------------------------------------------------------------

<S>                    <C>                    <C>               <C>                   <C>
Common Stock,
 par value $.01        1,118,089(2)           $7.973            $8,914,908            $2,478.34

----------------------------------------------------------------------------------------------------
</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 SIS Bancorp, Inc. ("SIS") into options to purchase Common Stock of the
Company pursuant to an Agreement and Plan of Merger, dated as of July 20, 1998,
as amended, between the Company and SIS.

(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. ss. 230.462.




<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.
         333-65031) filed on September 30, 1998.

                 (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.


                                      II-1


<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 ss.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.


                                      II-2


<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):

         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 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     SIS Bancorp, Inc. Director Stock Option Plan              (2)

         99.2     SIS Bancorp, Inc. Management  Stock Option Plan           (2)

         --------------

         (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 Quarterly Report on Form
                  10-Q for the three months ended June 30, 1996 filed by SIS
                  Bancorp, Inc. with the Commission (Commission File No.
                  0-20809).


                                      II-3


<PAGE>   6



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 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.


                                      II-4


<PAGE>   7



                                   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 31st day of
December 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                         December 31, 1998
----------------------------------------
Robert P. Bahre
Director


/s/ Peter J. Baxter                         December 31, 1998
----------------------------------------
Peter J. Baxter
Vice Chairman, Executive Vice President
 and Chief Operating Officer


/s/ P. Kevin Condron                        December 31, 1998
----------------------------------------
P. Kevin Condron
Director


/s/ Everett W. Gray                         December 31, 1998
----------------------------------------
Everett W. Gray
Director

                                      II-5


<PAGE>   8



/s/ Andrew W. Greene                        December 31, 1998
----------------------------------------
Andrew W. Greene
Director


/s/ Katherine M. Greenleaf                  December 31, 1998
----------------------------------------
Katherine M. Greenleaf
Director


/s/ Douglas S. Hatfield                     December 31, 1998
----------------------------------------
Douglas S. Hatfield
Director


/s/ Dana S. Levensen                        December 31, 1998
----------------------------------------
Dana S. Levensen
Director


/s/ Robert A. Marden, Sr.                   December 31, 1998
----------------------------------------
Robert A. Marden, Sr.
Director


/s/ Philip A. Mason                         December 31, 1998
----------------------------------------
Philip A. Mason
Director


/s/ Malcolm W. Philbrook, Jr.               December 31, 1998
----------------------------------------
Malcolm W. Philbrook, Jr.
Director


/s/ Pamela Plumb                            December 31, 1998
----------------------------------------
Pamela Plumb
Director


/s/ Seth Resnicoff                          December 31, 1998
----------------------------------------
Seth Resnicoff
Director


                                      II-6


<PAGE>   9




/s/ William J. Ryan                         December 31, 1998
----------------------------------------
William J. Ryan
Chairman, President and Chief
 Executive Officer
 (principal executive officer)


/s/ Curtis M. Scribner                      December 31, 1998
----------------------------------------
Curtis M. Scribner
Director


/s/ Paul R. Shea                            December 31, 1998
----------------------------------------
Paul R. Shea
Director


/s/ John E. Veasey                          December 31, 1998
----------------------------------------
John E. Veasey
Director


/s/ Peter J. Verrill                        December 31, 1998
----------------------------------------
Peter J. Verrill
Executive Vice President, Chief
 Financial Officer and Treasurer
 (principal financial and accounting 
 officer)


                                      II-7
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1

                                                           Registration No. 333-
                                                           Filed January 4, 1999

                       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 July 20, 1998, as
 amended, between the Registrant and SIS Bancorp, Inc. ("SIS"), upon conversion
 of outstanding options to purchase Common Stock of SIS issued by SIS under its
        Director Stock Option Plan and its Management Stock Option 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)
2

                         CALCULATION OF REGISTRATION FEE
----------------------------------------------------------------------------------------------------

    Title of
   Securities            Amount         Proposed Maximum     Proposed Maximum         Amount of
      to be              to be           Offering Price         Aggregate          Registration Fee
   Registered         Registered(1)        Per Share(3)      Offering Price(3)
----------------------------------------------------------------------------------------------------
Common Stock,
 par value $.01        1,118,089(2)           $7.973            $8,914,908            $2,478.34

----------------------------------------------------------------------------------------------------
(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 SIS Bancorp, Inc. ("SIS") into options to purchase Common Stock of the
Company pursuant to an Agreement and Plan of Merger, dated as of July 20, 1998,
as amended, between the Company and SIS.

(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. ss. 230.462.
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.
         333-65031) filed on September 30, 1998.

                 (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.

                                      II-1
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 ss.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.

                                      II-2
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 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     SIS Bancorp, Inc. Director Stock Option Plan              (2)

         99.2     SIS Bancorp, Inc. Management  Stock Option Plan           (2)

         --------------

         (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 Quarterly Report on Form
                  10-Q for the three months ended June 30, 1996 filed by SIS
                  Bancorp, Inc. with the Commission (Commission File No.
                  0-20809).

                                      II-3
6

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 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.

                                      II-4
7

                                   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 31st day of
December 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                         December 31, 1998
----------------------------------------
Robert P. Bahre
Director

/s/ Peter J. Baxter                         December 31, 1998
----------------------------------------
Peter J. Baxter
Vice Chairman, Executive Vice President
 and Chief Operating Officer

/s/ P. Kevin Condron                        December 31, 1998
----------------------------------------
P. Kevin Condron
Director

/s/ Everett W. Gray                         December 31, 1998
----------------------------------------
Everett W. Gray
Director

                                      II-5
8

/s/ Andrew W. Greene                        December 31, 1998
----------------------------------------
Andrew W. Greene
Director

/s/ Katherine M. Greenleaf                  December 31, 1998
----------------------------------------
Katherine M. Greenleaf
Director

/s/ Douglas S. Hatfield                     December 31, 1998
----------------------------------------
Douglas S. Hatfield
Director

/s/ Dana S. Levensen                        December 31, 1998
----------------------------------------
Dana S. Levensen
Director

/s/ Robert A. Marden, Sr.                   December 31, 1998
----------------------------------------
Robert A. Marden, Sr.
Director

/s/ Philip A. Mason                         December 31, 1998
----------------------------------------
Philip A. Mason
Director

/s/ Malcolm W. Philbrook, Jr.               December 31, 1998
----------------------------------------
Malcolm W. Philbrook, Jr.
Director

/s/ Pamela Plumb                            December 31, 1998
----------------------------------------
Pamela Plumb
Director

/s/ Seth Resnicoff                          December 31, 1998
----------------------------------------
Seth Resnicoff
Director

                                      II-6
9

/s/ William J. Ryan                         December 31, 1998
----------------------------------------
William J. Ryan
Chairman, President and Chief
 Executive Officer
 (principal executive officer)

/s/ Curtis M. Scribner                      December 31, 1998
----------------------------------------
Curtis M. Scribner
Director

/s/ Paul R. Shea                            December 31, 1998
----------------------------------------
Paul R. Shea
Director

/s/ John E. Veasey                          December 31, 1998
----------------------------------------
John E. Veasey
Director

/s/ Peter J. Verrill                        December 31, 1998
----------------------------------------
Peter J. Verrill
Executive Vice President, Chief
 Financial Officer and Treasurer
 (principal financial and accounting 
 officer)

                                      II-7