Perhaps the most surprising and quietest - hit on network television is the CBS detective series "Diagnosis Murder."

The Dick Van Dyke vehicle finished in a tie for 22nd in the ratings last week, and its audience has grown more than any other returning series this season.Not bad for a guy who first came to CBS in "The Dick Van Dyke Show" almost 37 years ago.

CBS's competitors, of course, are quick to point out that "Diagnosis Murder" skews old - the vast majority of its audience is over the age of 50. But Moonves isn't willing to qualify the show's success.

"If people would realize that older viewers are valuable and they count and they buy things, no one would question it," he said. "I think it's significant. It's counter-programming at its best. What else would be better against Jerry Seinfeld?"

The CBS president praised the program as "one of the most creative shows on television. Every week they come up with a different gimmick."

"It's growing every week. The truth of the matter is that `Diagnosis Murder' did not get one single promo spot during the Olympics. There is a real solid audience. It's growing. It's a fun show to watch. And Dick Van Dyke is one of our most valuable stars."

ON THE OTHER HAND: At this point, it's extremely questionable as to whether the new CBS series "Four Corners" will ever air again.

The show's debut last week was less than sparkling - a 6.9 rating good for 65th place overall. And early indications are that those numbers dropped significantly this week.

"We are very pleased with how `The Closer' has done and `Candid Camera' has done," Moonves said. "Obviously, `Four Corners' has had less-than-spectacular results and we are looking at what the future of that show is. And it probably is not very bright right now."

In a business where executives are loathe to say anything negative about any of their shows, that's tantamount to admitting "Four Corners" is already dead as a door-nail.

Moonves, on the other hand, said he remains "guardedly encouraged" about "Public Eye with Bryant Gumbel," which moved to Tuesdays this week after undergoing some revamping.

"I think it is definitely a better product," he said. "I want to hang in there with this show. I think it has great potential."

While there have been reports that CBS would insert a movie on Tuesdays at 8 p.m., Moonves said he wants to avoid doing that just yet.

"I want to give Bryant a real run there," he said. "We're talking about all possibilities. I hope to be able to do something at o'clock without putting a movie in there right away."

(Now that sounded like a death knell for "Four Corners.")

OTHER SHOWS: Don't be surprised if "Gregory Hines," which was heavily hyped during the Olympics and still failed to attract much of an audience last Friday, doesn't survive much longer.

"We were disappointed in the initial results," Moonves said. "We thought it was a very good episode. It was promoted."

- A couple of other shows in trouble are "George & Leo" and "Brooklyn South." The most positive thing Moonves could say about their futures was, "We haven't made any decisions."

The lagging ratings of "Brooklyn South" remain a particular disappointment for Moonves, who saw the Steven Bochco-produced drama as one of his great hopes this season.

"We think it's a very good show," he said. "Is there an audience for it? I don't know."

ADDED VALUE: While the folks at CBS aren't overly thrilled with the 16.2 rating they got from Nagano - they had expected a 19.5 - they aren't unhappy either. And Moonves was quick to point out the benefits that went beyond simply the Olympic numbers.

"Even with non-Olympic programming, CBS posted across-the-board growth vs. last February," Moonves said. The network was up 8 percent in households and viewers 25-54 and 7 percent in viewers 18-49.

He also pointed to:

- The Grammy Awards, which were "greatly helped by the Olympics." They had their highest ratings in five years and attracted more young viewers than usual.

- The Olympics provided a big boost for the "Late Show with David Letterman," which beat "The Tonight Show" during both weeks of Games coverage and has showed improved ratings since they ended.

"I think Letterman was rediscovered and reinvigorated," Moonves said. "That was important for us.

"I think there's been a halo effect that carried over into last week. I think any of you who watched David during the Olympics saw him at his best. I think he is at his best when he feels good about his chances of winning."

- The 13 CBS-owned stations were up 88 percent in prime time over February 1997. And the owned stations provide the bulk of a network's income.

- Then there were all those promotional spots for "Everybody Loves Raymond" that aired during the Games.

"I think Ray Romano is going to be helped a great deal in terms of recognition," Moonves said. "I think `Everybody Loves Raymond' is up there with the best comedies on television.

"We want to establish Ray Romano as the next Jerry Seinfeld or Tim Allen and put him in that league."

- The promotional spots also helped CBS with the return of "Dr. Quinn, Medicine Woman" and the premiere of "Candid Camera."

"I think it relaunched our Saturday night. We had our best Saturday night (with regular programming) in a number of months," Moonves said. "And it enabled us to get our Friday (7-8) in good order."