Long in gestation, Jim Carroll's confessional diaries finally make it to the screen, albeit in a film not entirely sure of itself. Carroll was writing for his adolescence (the 60s); the film - judging by its score, its references - appears to be contemporary. The two do not always sit comfortably, and occasionally, as in the drugged-up basketball game scored to The Doors, seems to be having its cake and trying to consume it as fast as it can.

Carroll is one of a New York streetgang. His mother is struggling to bring him up on her own. Jim and his cohorts are more content scamming for money or sniffing cleaning fluid. Only at basketball do they excel, while Jim gives reign to his more artistic impulses by compulsively writing thought and poetry in a school exercise book.

Of course, enough is never enough, and ultimately he's thrown out of home and takes to the streets, doing drugs, robbing for drugs, and, finally, hustling men for money for drugs.

There is a problem with films about drugs, and that is, while they might be a bag o'laughs to take, watching people shoot up is at best enervating. It takes a special example indeed to hold an audience, and The Basketball Diaries is no Drugstore Cowboy. Despite (because of?) their patent artificiality, junky Matt Dillion's visions of ecstasy were at least credible; debutante director Scott Kalvert (a vet of rap videos and TV's Fresh Prince of Bel Air) has the young hero bare his chest and run ecstatically through a field of flowers, or at least grimace manfully in the rain. Whether this is or is not indicative of sustained drug abuse, who can say?

The resultant film is thus split into two very definite halves, of which the first is by some distance the best. Carroll's slide from rebellious-teen to street-scum is well handled. The male bonding is both authentically macho and surprisingly homoerotic, and only slips into mawkish when we get to visit with their skinny, grey-faced friend Bobo (Alexander Gaberman), who is dying of leukaemia.

The second, though, is the usual mix of needles, dives, sallow-faced users and, inevitably, gaol. Sadly it's all very much been-there-done-that, and given we know the outcome (that's the real Carroll in an uncredited cameo) offers scant reward where suspense is concerned.

Still, the film is at least powered by a heavy-duty performance from DiCaprio, the youngster they insist on calling the new Brando. His physical similarity to the real Carroll is sometimes uncanny. But good as he is there is a sense of deja vu about it all. (Apparently the script was previously developed for Eric Stoltz, (ironically) Matt Dillon and (irony of ironies) River Phoenix.) There is able, albeit variable, support by Lorraine Bracco as the mother, James Madio, and Mark Wahlberg (aka Marky Mark) who, for all he has only one dimension, at least plays up to it. Juliette Lewis's uncredited $15-a-blow-job smackhead, on the other hand, is hysterical.

What we expected from Carroll was surely more than just another 'Just Say No' movie, but this has none of the ambiguity of the much better Van Sant picture, that's for sure. Still, Kalvert at least knows how to move a camera, and you do get to hear the Jim Carroll Band's brilliant 'People Who Died' on the soundtrack, so it's not without its compensations.