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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">UNITED STATES<br> SECURITIES AND EXCHANGE COMMISSION</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">WASHINGTON, D.C. 20549</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">FORM&nbsp;8-K</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">CURRENT REPORT<br> Pursuant to Section&nbsp;13 or 15(d)&nbsp;of the Securities Exchange Act of 1934</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Date of Report (Date of Earliest Event Reported):&nbsp;&nbsp;&nbsp;&nbsp; <b>May&nbsp;14, 2013</b></font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">Cogent Communications Group,&nbsp;Inc.</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Exact name of registrant as specified in its charter)</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Delaware</font></b></p>    </td>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">1-31227</font></b></p>    </td>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">52-2337274</font></b></p>    </td>   </tr>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(State or other jurisdiction of incorporation)</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Commission File Number)</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(I.R.S. Employer <br>   Identification No.)</font></p>    </td>   </tr>  </table>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">1015 31st St. NW, Washington, District of <br>   Columbia</font></b></p>    </td>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;"><br>   20007</font></b></p>    </td>   </tr>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Address of principal executive offices)</font></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Zip Code)</font></p>    </td>   </tr>  </table>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Registrant&#146;s telephone number, including area code:&nbsp;&nbsp;&nbsp;&nbsp; <b>202-295-4200</b></font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Not Applicable</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Former name or former address, if changed since last report</font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Check the appropriate box below if the Form&nbsp;8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:</font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Written   communications pursuant to Rule&nbsp;425 under the Securities Act (17 CFR   230.425)</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Soliciting   material pursuant to Rule&nbsp;14a-12 under the Exchange Act (17 CFR   240.14a-12)</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Wingdings" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Pre-commencement   communications pursuant to Rule&nbsp;14d-2(b)&nbsp;under the Exchange Act (17   CFR 240.14d-2(b))</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Pre-commencement   communications pursuant to Rule&nbsp;13e-4(c)&nbsp;under the Exchange Act (17   CFR 240.13e-4(c))</font></p>    </td>   </tr>  </table>
<p style="margin:0in 0in .0001pt .25in;text-indent:-.25in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><a name="PB_1_080806_7056"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></a></p>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.</font></b></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Jeffrey Karnes, Chief Revenue Officer and Vice President of Global Sales, left Cogent, effective May&nbsp;14, 2013.</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">2<a name="PB_2_080831_5335"></a></font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">SIGNATURES</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.</font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Cogent   Communications Group,&nbsp;Inc.</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">May&nbsp;14,   2013</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">By:   </font></p>    </td>
<td width="45%" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:45.66%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">/s/David   Schaeffer</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Name:   David Schaeffer</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Title:   Chairman and Chief Executive Officer</font></p>    </td>   </tr>  </table>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><a name="PB_3_080843_5796"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></a></p>
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{"company-data": {"conformed-name": "COGENT COMMUNICATIONS GROUP INC", "cik": "0001158324", "assigned-sic": "7372", "irs-number": "522337274", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-31227", "film-number": "13839529"}, "business-address": {"street1": "1015 31ST STREET", "city": "WASHINGTON", "state": "DC", "zip": "20007", "phone": "2022954200"}}
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
Date of Report (Date of Earliest Event Reported):
May 14, 2013
Cogent Communications Group, Inc.
(Exact name of registrant as specified in its charter)
Delaware
1-31227
52-2337274
(State or other jurisdiction of incorporation)
(Commission File Number)
(I.R.S. Employer
Identification No.)
1015 31st St. NW, Washington, District of
Columbia
20007
(Address of principal executive offices)
(Zip Code)
Registrant's telephone number, including area code:
202-295-4200
Not Applicable
Former name or former address, if changed since last report
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:
o
Written   communications pursuant to Rule 425 under the Securities Act (17 CFR   230.425)
o
Soliciting   material pursuant to Rule 14a-12 under the Exchange Act (17 CFR   240.14a-12)
o
Pre-commencement   communications pursuant to Rule 14d-2(b) under the Exchange Act (17   CFR 240.14d-2(b))
o
Pre-commencement   communications pursuant to Rule 13e-4(c) under the Exchange Act (17   CFR 240.13e-4(c))
Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.
Jeffrey Karnes, Chief Revenue Officer and Vice President of Global Sales, left Cogent, effective May 14, 2013.
2
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
Cogent   Communications Group, Inc.
May 14,   2013
By:
/s/David   Schaeffer
Name:   David Schaeffer
Title:   Chairman and Chief Executive Officer