Peter Iovino, Dreamworks Pictures
Reese Witherspoon and Mark Ruffalo mix it up in "Just Like Heaven."

"Just Like Heaven" offers further proof that a film really can get by on the charms of its stars. However, that this comedy-fantasy just gets by when it has stars as charming as Reese Witherspoon and Mark Ruffalo also shows that it has a few problems.

For one thing, it isn't nearly as funny as it should be. While it has a generally likable air, "Heaven" contains far more smile-worthy than chuckle-worthy moments.

And at one point, the film gets sidetracked and the supporting characters threaten to take over the whole thing (among the culprits is "Napoleon Dynamite" himself, Jon Heder). But the leads are far more interesting. They're who we really want to see.

Ruffalo is especially good as David Abbott, a landscape architect still reeling after death of his wife. David has recently sublet a scenic Bay Area apartment where he's content to mope about. But he soon discovers another tenant there — the spirit of a woman telling him to leave. As it turns out, she's Elizabeth Masterson (Witherspoon), a young physician who was renting the apartment before him.

At first, David does everything he can to rid himself of this spectral pest, who seems to turn up at the worst times. But as he gets to know more about Elizabeth, he becomes determined to find out why she's still lingering and what he can do to help her "pass on" — wherever that may lead her.

To his credit, director Mark Waters ("Mean Girls") does keep things moving quickly. In fact, the whole thing flies by so fast that you may not notice some of the more gaping plot holes.

What he — and the film — have going for them is the pairing of Witherspoon and Ruffalo. Their characters' bickering has an old-fashioned dynamic to it, and their romance of sorts is sweet and appealing.

The movie does spend a little too much time building up subplots, which feature characters played by Donal Logue and Dina Waters. And fans of Heder may be a little disappointed by his performance here. He's really not onscreen much time, and not all that amusing as he offers such surf-dude lingo as "awesome!"

"Just Like Heaven" is rated PG-13 for scattered use of profanity, brief drug content (including hypodermic use), brief partial male nudity (done for laughs), some off-color humor and suggestive comments, and two brief scenes of violence (fisticuffs and vehicular violence, overheard). Running time: 102 minutes.