“The Bucket List” operates on the hope that two beloved stars rubbing their signature screen personas together can spark warm, fuzzy box office magic. I wouldn’t count on it. Stars or no, it is an open question whether audiences will flock to a preposterous, putatively heartwarming buddy comedy about two men diagnosed with terminal cancer living it up in their final months.

The geezers chafing at death’s doorstep are Edward Cole (Jack Nicholson) and Carter Chambers (Morgan Freeman), cancer patients who meet cute in the room they share in a hospital owned by Edward. A greedy billionaire health care mogul, Edward is a victim of his own ruthless cost-cutting program that decrees two to a room in his cramped establishment.

Obviously, no billionaire in his right mind would endure such humiliation in an institution he is knowingly bleeding to death; he would have his own deluxe private suite somewhere else. Edward, however, does have gourmet food supplied by his obedient assistant Thomas (Sean Hayes), which he lustily consumes until chemotherapy takes away his appetite along with his hair.

Slipping into their stock screen personas of rampaging fool (Mr. Nicholson) and pious wise man (Mr. Freeman), neither actor adds a note that we haven’t seen before. Given less than a year to live, Edward and Carter flee the hospital to board Edward’s private jet for a final blowout underwritten by Edward.

Along the way they become best pals who help each other learn the usual lessons about living life to the fullest. The movie strenuously denies medical reality. As they undertake their journey, both men, in temporary remission, appear as robust as the rejuvenated seniors in “Cocoon.”

Their initial adventures, like sky diving and race car driving, are high-adrenaline stunts embraced with macho zeal; they even visit a tattoo parlor. As they follow an itinerary that takes them to the south of France, the Pyramids, the Taj Mahal, the Himalayas and Hong Kong, these stopovers, obviously filmed on a soundstage, have all the reality of snapshots photographed in front of travel posters.

On the sexual front, the happily married Carter demurs when opportunity presents itself. But nothing has ever prevented Edward, who has been married and divorced four times, from pursuing continuous novelty. The movie mercifully spares us the spectacle of Mr. Nicholson, whalelike at 70, in full rutting mode.

Directed by Rob Reiner from a sketchy screenplay by Justin Zackham, “The Bucket List” fails its stars in fundamental ways. Mr. Nicholson has played wealthy rogues before (most recently in “Something’s Gotta Give”), but this particular bon vivant is unsalvageably repellent. The actor’s frantic mugging, guffawing and eyebrow twitching only underscore the character’s pompous self-satisfaction. By the time the movie allows Edward a token gesture of humanity (his guilt-stricken attempt to reunite with an estranged daughter he cruelly betrayed), it is too little too late.

Carter is the one who initially brings up the notion of “the bucket list,” a roster of must-have experiences to be pursued before “kicking the bucket.” We are asked to accept that this dignified sage has been happily toiling as an auto mechanic for 46 years after forgoing his higher education to support a family. Anyone this articulate and composed would have risen far above day-laborer status.

Largely self-taught, Carter keeps himself in mental shape by watching “Jeopardy!” and competing out loud with the contestants. During their travels he is a font of geographic and historical trivia.

For all the kindly gravity he puts into the role, Mr. Freeman cannot begin to make you believe that a quiet family man like Carter would abandon his loyal wife (Beverly Todd) during his final months of life to go on a spree with a rascally egomaniac. I don’t imagine Mr. Freeman believes it either.

Saddest of all, the professed spiritual goals on the pair’s checklist of things to do — “laugh till you cry,” “witness something majestic” — are the kind of pallid bromides found in the pages of a quickie self-help book: “I’m Not O.K., and Neither Are You.”

“The Bucket List” is rated PG-13 (Parents strongly cautioned). It has off-color dialogue.

THE BUCKET LIST

Opens on Tuesday in New York, Los Angeles and Toronto.

Directed by Rob Reiner; written by Justin Zackham; director of photography, John Schwartzman; edited by Robert Leighton; music by Marc Shaiman; production designer, Bill Brzeski; produced by Craig Zadan, Neil Meron, Alan Greisman and Mr. Reiner; released by Warner Brothers Pictures. Running time: 1 hour 38 minutes.

WITH: Jack Nicholson (Edward Cole), Morgan Freeman (Carter Chambers), Sean Hayes (Thomas), Rob Morrow (Dr. Hollins) and Beverly Todd (Virginia).