Carson says he had just finished a game of tennis when he learned of a tabloid report that claimed he is seriously ill.
The National Enquirer was reporting that the television legend, at age 76, had become a virtual recluse, shut up on his yacht with only his wife and the yacht's crew.
The supermarket tabloid went on to say that Carson has "been grappling with killer emphysema for several years and wants to stay out of the public eye."
Carson, issuing a statement through Carson Productions spokesman Jeff Sotzing, says he does have emphysema but "I'm dealing with it the best I can and it is not causing me any major problems."
Sotzing added that Carson is far from sidelined and played tennis at least twice this week. "He's in great shape," says Sotzing.
He declines to give any details of Carson's medical condition, other than to say the entertainer has not been hospitalized.
Carson underwent quadruple bypass heart surgery three years ago.
Many cases of emphysema, which causes shortness of breath, can be attributed to cigarette smoking. It cannot be cured, but if caught early, its progression can be halted.
Carson, who smoked on the air for many years, was the host of NBC-TV's "The Tonight Show Starring Johnny Carson" from 1962-92. He has seldom been seen in public since his retirement.
When he's not spending time at his bluffside estate in Point Dume, Calif., Carson cruises in his custom-built, triple-decker, 130-foot yacht.
In an Esquire magazine interview earlier this year, Carson said he was perfectly content to be out of the public eye, living quietly in a large Malibu home he shares with his wife, Alexis, playing cards with friends and spending time on his yacht.