Oh, to be 16, to have not one, but three best friends so loyal they don't laugh you off the planet for using words like "sisterhood," and to time-share a pair of magical blue jeans!

As an exercise in wish fulfillment, The Sisterhood of the Traveling Pants, based on a book of the same name, is probably fun for girls of a certain age. What awkward 12-year-old, for example, wouldn't feel secretly exalted by the possibility of true love, a few years down the line, with a hunky Greek fisherman whom she's reeled in just by falling off a dock? (With a Hollywood mixture of virtuoso English and a heavy accent, the soulful hunk says things like, "Others try to hide their beauty 'cause they want the world to see something kelse.")

That's how the magic jeans work for Lena (Alexis Bledel), who wears a tidy ponytail to Greece, stays with her grandparents there for a couple of months, and returns with ravishing loose curls. The jeans-which Lena and the other girls find in a second-hand store just before parting ways for the summer, and which fit all four perfectly, despite their varying heights and weights-spend a week with each of them in turn.

Bridget (Blake Lively), an overachieving extrovert, goes to a soccer camp in Baja and, with the help of the jeans, scores a tousled young coach. In an after-school-special plot twist, her "first time" with him on the beach leaves her feeling empty. All's well that ends well, though, when the returning Columbia student shows up in her neighborhood after camp to ask that she give him a chance when she's a little older.

Carmen and Tibby don't have it quite as good. Carmen (America Ferrera), proudly Puerto Rican on her mother's side, heads south and discovers that her absentee father has become a white-bread-eating, grace-saying Protestant engaged to a high-strung blond with two kids of her own. Tibby (Amber Tamblyn), the one who's left behind in Maryland, spends the summer pricing shampoo at a Wal-Mart look-alike and working on a "suckumentary" (interviewing people whose lives suck). But the magical jeans give Carmen the courage to confront her father, and they bring briefly into Tibby's life a young pest of a friend, Bailey (Jenna Boyd), whose subsequent death from leukemia teaches Tibby life lessons.

This movie, as you may suspect, tries to be everything-light and substantial, dreamy and real. It tries, and it fails. In Tibby's story, its depiction of mega-stores as mind- and soul-numbing feels trendy rather than critical. That only the two conventionally pretty friends' adventures are romantic is difficult to overlook. Most egregious, though, is the use of leukemia as a justification for precocious speeches. Gazing up at the sky with Tibby, Bailey explains that she's not afraid of death; she just wants "time to figure out who I'm supposed to be, time to find my place in the world before I have to leave it." Blech. It's hard to admire the heart in a movie that makes me feel heartless.