"Breathing Easy," airing at 9 p.m. tonight on Channels 26 and 32, on the eve of the Great American Smokeout, is a slick and sprightly effort to combat the appeal of cigarettes and smoking among the nation's teen-agers. Both the program and the Smokeout share the American Heart and Lung associations and the American Cancer Society as sponsors.

Whether its producers (WQED-Pittsburgh) intended it or not, the program is actually aimed more at preteens, more at the 9-to-12 set than at their older brothers and sisters -- and even though today's fifth graders are tomorrow's smoking teens, the late time slot for this one-hour special may have done it out of its best audience.

That, however, is about the worst that can be said for this star-studded, sugar-coated, high-quality approach to radicalizing youngsters to the benefits of non-smoking.

Who better than Top 40 disc jockey Casey Kasem, for instance, his voice and face as familiar as Mom's and Dad's, to emcee large segments of the program? Or who better to come on to the teens than "St. Elsewhere" hunk Mark Harmon, whose puppy-dog eyes and winsome smile could convince almost any female under the age of about 90 of almost anything?

In a parody talk show interview with Joan ("Knots Landing") Van Ark, Harmon talks about his dad, the ex-Michigan All-American and later sportscaster who was once the Chesterfield Man. "And," he says, "you're talking about a guy who grew up with idols like John Wayne, Gary Cooper, Humphrey Bogart, Montgomery Clift, and all those guys except for my father -- who stopped smoking -- are dead now . . ."

The younger Harmon once got a producer to rewrite a role he was playing, making the character a nonsmoker.

Some other nonsmokers in the program: Placido Domingo, Menudo, Sting, Linda Evans, Victoria Principal, Loretta Swit, Meredith Baxter Birney, Robin Williams, John Travolta, Johnny Mathis, Cathy Rigby, Prince Charles, Ricky Schroeder, Scott Baio, Joe Piscopo, Morgan Fairchild, Michael Jackson . . . and lots more.

Then there's "Diner's" Paul Reiser on the esthetic effects of smoking: "If you yawn and flies die, that's very, very bad breath . . ."

"Breathing Easy" also features LeVar ("Reading Rainbow") Burton as the host of a 15-minute quiz show spoof called "You Bet Your Lungs," and "E.T.'s" Robert Macnaughton in a sitcom segment.

There is some spectacular break-dancing by a group called the Kingsley Robonic Tic-Toccers from Pittsburgh, and a quick lesson in subliminal advertising by the founder of DOC (Doctors Ought to Care).

That group has produced its own ads, one of which proclaims: "Arctic lungs -- guaranteed to make you coooool . . . as a corpse." From another: "You've coughed long enough, Baby." This goes along with DOC's celebrity tennis tournament -- "Emphysema Slims."

DOC's newest spot is a classy parody of Randy Newman's "Short People":

Smo-kers have got nobody to love

They got smoke in their clothes

and smoke in their hair

They drop those smelly little butts

just everywhere

They've got cinder ashes

that they flick, flick, flick

They've got cigarette smoke that makes me sick, sick, sick

Well I, I don't want no smo-kers around me . . .