March 9 (Bloomberg) -- CBS Corp. said it expects a 30 percent increase in revenue from online advertising for college basketball’s postseason tournament.

Online ad revenue will be about $30 million, up from $23 million a year ago, and Internet ad inventory is almost sold out, said Jason Kint, senior vice president and general manager for CBSSports.com. The network is in the seventh year of an 11-year, $6 billion contract that gives it broadcast and online rights for the NCAA tournament.

General Motors Corp., AT&T Inc. and Coca-Cola Co. are among the online marketers of this year’s tournament, known as “March Madness,” even as companies scale back spending with the economy in recession.

“We are seeing the same challenges that the rest of the online media are seeing as far as overall ad sales, but March Madness on Demand, based on the numbers, had a strong sales year,” Kint said in a telephone interview.

Advertisers spent $643 million overall on the tournament last year, up 24 percent from $520 million in 2007, the Wall Street Journal said, citing TNS Media Intelligence, a unit of ad holding company WPP.

CBS’s March Madness on Demand gives online viewers free access to live and archived National Collegiate Athletic Association men’s tournament games. The tournament is a single- elimination tournament featuring 65 college teams.

Comcast Corp., the largest U.S. provider of cable service, agreed to sponsor the CBSSports.com Web site’s “boss button,” which lets viewers at work hide their viewing from supervisors. The button received 2.5 million clicks last year, Kint said.

CBS’s interactive division, which purchased Cnet Networks Inc. for $1.8 billion in July, has 220 million monthly unique visitors across its online platforms, Kint said.

“With 130 million people that watch the NCAA tournament, we only reached 4.8 million of them online last year,” he added.

Following a play-in game on March 17, the first round of the NCAA tournament is March 19. The national title game is April 6 in Detroit.

To contact the reporter on this story: Mason Levinson in New York at mlevinson@bloomberg.net.

Last Updated: March 9, 2009 17:09 EDT