CBS Corp. confirmed on Thursday the acquisition of CNET Networks Inc. for $1.8 billion, in one of the biggest deals to strike the Internet world in the recent years. The investment will increase the television broadcaster’s online audience on a market rapidly expanding market.

The acquisition of CNET Networks, which owns several websites, such as News.com, TV.com or GameSpot, will turn CBS in one of the 10 most popular Internet companies in the U.S., with 54 million unique users per month, and 200 million users worldwide.

CBS President and Chief Executive Officer Leslie Moonves said in a statement that there are only few opportunities as profitable as this one, and that CNET Networks will add “a tremendous platform” at CBS’s entertainment, news, sports, music and information content, which will appeal to a whole new global audience.

The deal means $11.50 a share for CNET shareholders, a 54 percent premium to Wednesday’s $7.95 a share closing price, the companies announced in a statement today. The deal, which is expected to complete in the third quarter of this year, has been unanimously approved by the CNET board, the company said in a joint statement with CBS.

CBS, which reported $406 million in revenues in 2007, seeks new opportunities with this acquisition, including in terms of overseas audience, especially China, the company added in its statement.

In its turn, CNET chief executive Neil Ashe said they were thrilled of this deal, which combines their interactive media experience with CBS’s world-class content, adding that his company currently operates premium online brands which serve “the most sought after online audiences.”

A representative for the hedge-fund firm Jana Partners, a group of investors from New York who has been trying to get a piece of CNET after the companies shares went down last year by using a proxy fight to get directors elected to the company’s board, could not be reached for comments.