by Marilyn Beck and Stacy Jenel Smith Demi Moore put smiles on the faces of aging women everywhere in June, when the gorgeous 40-year-old scene stealer swept into the "Charlie's Angels: Full Throttle" premiere with her action movie star ex hubby, Bruce Willis, on one arm and and her hunky boyfriend, 25-year-old Ashton Kutcher, on the other."Face it, gals, this is a fantasy come true for all of us!" chirped a thirtysomething studio insider at the sight.

Then celeb watchers caught on to a romance brewing between Cameron Diaz, who turns 31 in August, and Justin Timberlake, who is eight years her junior -- and what a sizzling summer it became for older women-younger man couplings.

The fact is, breaking the age barrier is a favorite sport among the celebrity elite -- not just this year, but every year.

In fact, just one summer ago, when he was a mere lad of 21, Justin was raising eyebrows via a rumored romance with then-36-year-old Janet Jackson. Perhaps after that excruciatingly over-publicized romance with his not-so innocent, yet-inexperienced peer Britney Spears, Justin's been in the market for worldly women.

As diet guru Nikki Haskell remarked, after her pal Joan Collins married 32-years-younger theatrical-company manager Percy Gibson, "Young guys appreciate someone who knows how to get around."

Certainly that's true in many cases in Hollywood, where there is no shortage of older women-younger man pairings:

Madonna is 10 years older than director hubby Guy Ritchie.

Former Miss America Vanessa Williams, 40, and her handsome husband, L.A. Lakers forward Rick Fox, 34, are one of the prettiest couples in Tinseltown.

Courteney Cox Arquette, 39, is eight years older than her best friend, David.

Original "Charlie's Angel" Jaclyn Smith is nine years older than hubby Bradley Allen.

Geena Davis' doctor spouse, Reza Jarrahy, is 15 years younger than the 47-year-old actress.

Julianne Moore, 42, has two children with live-in love, writer-director Bart Freundlich, 33. She admits she worries about losing him as she ages -- a common insecurity among women with younger spouses. But there's no denying the longevity of some of these couplings.

Susan Sarandon and 12 years-younger mate Tim Robbins have been together since 1988. She finds Tim, the father of her two teenage sons, in some ways, "older, more traditional than me."

And Goldie Hawn has been with five-years-younger Kurt Russell for two decades.

True love -- and great sex -- aside, there are all sorts of psychological factors behind celebrities' attraction to members of the opposite sex who represent a break in the age barrier. Those include not just older women with younger men, but older men with much-younger (as in an entire generation) women.

After all, these are "Look at me!" people, who make it their business to grab the attention of the public eye, and playing with cultural taboos is a sure way to do that. Also, there's the ego factor. Like average folks -- but vastly magnified -- celebrities of both genders find that there's a fountain of youth effect in partnering up with a tender young mate.

Especially good for such a transformation is the younger wife with whom to have or share babies.

How refreshed Harrison Ford has been looking in those pics with 23 years-younger girlfriend Calista Flockhart and her toddler son, for instance. And Warren Beatty went from over-the-hill playboy to "Daddy!" when he finally settled down with 21 years-younger wife Annette Bening and started having offspring. Catherine Zeta-Jones and their babies have been better than a face lift for rejuvenating Michael Douglas, who is 25 years older than his wife.

And when Paul McCartney really is 64, which will be in three years, his life won't be much like the picture envisioned in his and John Lennon's famous "When I'm Sixty-Four" song. Instead of settling into a rocker beside a wife who's "older, too" knitting by the fireside, he's on track to be romping around with his two year-old tot by beautiful 25-years-younger bride Heather Mills.

Obviously, this kind of setup is as much a fantasy come true for lots of guys as Demi's romp with her Boy Toy Ashton is for lots of women.

As Beverly Hills psychiatrist Dr. Carole Lieberman has pointed out, when enough celebs break the age barrier, it "normalizes things" for the rest of us, granting everyday people permission, in a way, to have older, or younger, love interests as well.