PASADENA, Calif. — CBS isn't exactly champing at the bit to compete against Jay Leno in prime time. Well, OK, CBS is pretty much champing at the bit to compete against Jay Leno's Monday-Friday, 9-10 p.m. talk show on NBC.

And the CBS staff is pretty darn excited about having David Letterman compete against Leno's "Tonight Show" successor, Conan O'Brien. After the first couple of months of that matchup, Letterman is beating O'Brien by a wide margin in total viewers. And he's pulled almost even in the competition for the younger demographics advertisers crave.

"We see this as a great opportunity. It's a sea-change in our business," CBS Entertainment President Nina Tassler said of NBC's decision to hand five hours of prime time over to Leno.

Not that she expects that anybody at NBC will ever admit that move was a mistake, even if the ratings are terrible.

"Well, first of all, whatever numbers, whatever ratings they get, they're going to declare a victory anyway. So it really doesn't matter," she said, eliciting laughter from the critics gathered to toss questions at her.

Not that she has any desire to handicap Leno's chances.

"No. I have no desire to do that," she said.

CBS's opportunity comes because it has been very successful with its weeknight, 9-10 p.m., MST dramas. "CSI: Miami," "CSI: NY" and "Numb3rs" win their time slots on Mondays, Wednesdays and Friday, respectively. "The Mentalist" — last season's biggest new show — has moved to 9 p.m. Thursdays. And the very-promising new show "The Good Wife" debuts at 9 p.m. Tuesdays in the fall.

"(Nine) o'clock has been a great business for us," Tassler said. "Our shows do very well."

She is particularly excited about "The Mentalist's" future.

"It generates billions of dollars for us in revenue, between foreign sales, syndication," she said. "(Nine) o'clock is a great business, and it's only going to boost Dave as well."

Leno could well surprise everyone, but he's not expected to come close to beating CBS's dramas in the ratings. NBC's decision was prompted by the fact that it can produce five "Jay Leno Shows" for what it would cost to produce one hourlong drama.

But that last hour of prime time has traditionally had a big influence on local late-night news ratings. Which isn't good news for NBC stations across the country.

And that last hour of prime time has carried over to the post-news programming. Which isn't good news for O'Brien.

And Letterman is clearly energized.

"He's at the top of his game," Tassler said. "He's very excited."