| Subsidiaries of COGENT COMMUNICATIONS GROUP, INC. | (Delaware corporation) | |
COGENT COMMUNICATIONS, INC. | (Delaware corporation) | |
| AC COMMUNICATIONS ACQUISITION CORP. (COGENT GREAT LAKES COMMUNICATIONS, INC. as of February 10, 2003) | (Delaware corporation) | |
| COGENT INTERNET, INC. | (Delaware corporation) | |
| ALLIED RISER COMMUNICATIONS CORPORATION | (Delaware corporation) | |
| ALLIED RISER OPERATIONS CORPORATION | (Delaware corporation) | |
| COGENT COMMUNICATIONS WORLDWIDE, INC. | (Delaware corporation) | |
| ALLIED RISER COMMUNICATIONS (NL) B.V. | (Netherlands corporation) | |
| ALLIED RISER COMMUNICATIONS CORPORATION OF CANADA INC. | (Nova Scotia corporation) | |
| SHARED TECHNOLOGIES OF CANADA INC. | (Canadian Federal corporation) | |
| FIBER SERVICES OF CANADA, LTD. | (Nova Scotia corporation) | |
| COGENT COMMUNICATIONS OF ARIZONA, INC. | (Delaware corporation) | |
| ALLIED RISER OF CALIFORNIA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF CALIFORNIA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF CONNECTICUT, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF D.C., INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF FLORIDA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF GEORGIA, INC. | (Delaware corporation) | |
| COGENT FIBER SERVICES OF GEORGIA, INC. | (Georgia corporation) | |
| COGENT COMMUNICATIONS OF ILLINOIS, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF KENTUCKY, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF LOUISIANA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF MARYLAND, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF MASSACHUSETTS, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF MICHIGAN, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF MINNESOTA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF MISSOURI, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF NEW JERSEY, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF NEW YORK, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF NORTH CAROLINA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF OKLAHOMA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF OHIO, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF PENNSYLVANIA, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF TENNESSEE, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF TEXAS, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF UTAH, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF VIRGINIA, INC. | (Virginia corporation) | |
| COGENT COMMUNICATIONS OF WASHINGTON, INC. | (Delaware corporation) | |
| COGENT COMMUNICATIONS OF WISCONSIN, INC. (at December 31, 2002) | (Delaware corporation) |
