Life-swapping is good for Dudley Moore. He's fresh as a kid again in "Like Father Like Son," a cheerful role-reversal comedy that finds the actor fairly capering through his first solid performance since he played the perpetual adolescent "Arthur." Suffice it to say, Moore isn't acting his age. He's chewing HubbaBubba and going deaf to heavy metal here as a middle-aged heart surgeon who unwittingly switches bodies with his teen-age son.

Moore starts out as the recently widowed Jack Hammond, a stuffy genius destined to become chief of staff at one of the world's leading high-tech hospitals. He's an archetypal authoritarian, a nag who expects his son Chris to follow in his footsteps by attending medical school. Chris, a kid who closes his eyes to dissect a frog, struggles to meet his father's standards, but is easily distracted by track and girls.

Kirk Cameron, who plays the eldest son on the TV comedy "Growing Pains," shines in his movie debut in the dual role of Chris. Cameron, with his living-room charisma and Campbell Soup Kid's face, is destined for Michael J. Foxdom. And Moore, with a hairdo like a moussed dust mop, is almost a heartthrob himself -- now that he's finally quit trying to be one.

Moore busses the boss' wife, but he has already flip-flopped, so it doesn't count. The petite actor goes on tiptoe to reach her. "Sorry, I'm normally a bit taller," he apologizes. It seems Moore is able to laugh at himself in this silly situation, a guileless, goofy one scripted by Lorne Cameron and Steven L. Bloom. The screen writers have come up with a simple-minded scenario, true, but it is enlivened with enough laughs to make up for the shortcomings.

After a hard day of heart surgery, Dr. Hammond mistakes the brain transference serum for the Tabasco sauce and mixes himself a Bloody Mary. He takes a sip, looks into his son's eyes and is shocked to see himself. Chris starts screaming, "I'm old! I'm old!" They ululate to Miles ("La Bamba") Goodman's witty musical score, which is something of a combo between "Nightmare on Elm Street" and "2001."

But Moore is soon boogying to MTV, playing air guitar, pleading with his "father" to keep a date with his dream girl. Cameron, believably stodgy, takes his date home early, while his "son" goes out and charges the limit on the gold card. High jinks continue until both the hospital board and the kids at school are thoroughly alienated. And predictably, the protagonists are coming to understand each other's strengths and problems.

Sean Astin, son of Patty Duke and John Astin, is solid as a sarcastic teen sidekick whose archeologist uncle discovered the serum among the Navajos. But enjoyable as they are, the kids take a back seat as director Rod Daniel of "Teen Wolf" fame rightly capitalizes on Moore's shenanigans. Daniel has made a bit of a transformation himself with this nicely paced generation bender. The movies have already swapped jobs, sexes and races. Age may be the last gap. Maybe they should have called this one "Old Like Me."

Like Father Like Son, at area theaters, is rated PG-13.