WASHINGTON, D.C., May 18, 2006 - Cogent Communications Group, Inc. (NASDAQ: CCOI) announced today that it plans to sell 12 million shares of its common stock in an underwritten public offering. The offering will consist of 4 million shares sold by the company and 8 million shares sold by selling stockholders. The shares sold by the selling stockholders represent approximately 29% of the shares held by Cogent's major investors. The underwriters will have an option to purchase up to an additional 15% of the shares offered to cover over-allotments, if any. Lehman Brothers and Bear Stearns will be acting as joint book-running managers on the offering, Thomas Weisel Partners will be acting as joint lead manager and Wachovia Securities and Friedman Billings Ramsey will be acting as co-managers.

Dave Schaeffer, Cogent's Chief Executive Officer, said that the offering would serve two purposes. "First, it increases the amount of Cogent's common stock available in the public markets. Second, it provides additional capital for Cogent to pursue its growth strategies."

This press release shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state.

This offering will only be made by means of a prospectus. Copies of the prospectus supplement and the accompanying prospectus can be obtained from:

Lehman Brothers Inc.

c/o ADP Financial Services

Prospectus Fulfillment

1155 Long Island Avenue

Edgewood, NY 11717

Fax: (613) 254-7268

Email: Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.

Bear, Stearns & Co. Inc.

c/o Prospectus Department

383 Madison Avenue

New York, NY 10179

Phone: 631-254-7129

Thomas Weisel Partners LLC

Prospectus Department

One Montgomery Street

San Francisco, CA 94104

FAX: 415-364-2799

Wachovia Securities

Equity Syndicate

375 Park Avenue, #4077

New York, NY 10152

Fax: (212) 214-5918

Friedman Billings Ramsey & Co., Inc.

Prospectus Department

1001 Nineteenth Street North

Arlington, VA 22209

Tel: (703) 469-1023

About Cogent Communications

Cogent Communications (NASDAQ: CCOI) is a multinational, Tier 1 facilities-based ISP. Cogent specializes in providing businesses with high speed Internet access and point-to-point transport services. Cogent's facilities-based, all-optical IP network backbone spans 14 countries and provides IP services in over 95 markets located in North America and Europe.

Cogent Communications is headquartered at 1015 31st Street, NW, Washington, D.C. 20007. For more information, visit www.cogentco.com. Cogent Communications can be reached in the United States at (202) 295-4200 or via email at Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser..

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Information in this release may involve expectations, beliefs, plans, intentions or strategies regarding the future. These forward-looking statements involve risks and uncertainties. All forward-looking statements included in this release are based upon information available to Cogent Communications Group, Inc. as of the date of the release, and we assume no obligation to update any such forward-looking statement. The statements in this release are not guarantees of future performance and actual results could differ materially from our current expectations. Numerous factors could cause or contribute to such differences. Some of the factors and risks associated with our business are discussed in Cogent's registration statements filed with the Securities and Exchange Commission and in its other reports filed from time to time with the SEC.

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