Popular misconception holds that River Phoenix was set to play the lead before tragically dying on the L.A. sidewalk. This is not entirely accurate. Phoenix was a big fan of the book, and as the film version entered various stages of readiness he was always the front runner. However, prior to his death, he had declined the role due to a combination of feeling he was too old to play a 15 year old, and trying to broaden his range with more adult roles.
After being nominated for an Oscar for Running on Empty (1988), MTV asked River Phoenix what he wanted to do next. He responded by pulling out a beat up paperback of "The Basketball Diaries" and stated "I wanted to play Jim Carroll." Later, the Los Angeles Times declared, "River Phoenix may have wanted it too much." Leonardo DiCaprio was a fan of Phoenix's.
Many links to The Sopranos - Lorraine Bracco (Dr Melfi) plays Jim's mom. Michael Imperioli (Christopher Moltisanti) plays the friend who dies of Leukemia. Vincent Pastore (Big Pussy) is the guy that gets vomited on whilst on the ferry.
Stephen Lang was offered the role of Jim's Basketball Coach named Swifty in the script. Lang declined citing the misrepresentation of the book in the script. The part was subsequently toned down as a result.
A drug consultant was hired for authenticity and was present on set. DiCaprio outlined how to talk like a Junkie to the Los Angeles Times. "The voice: you go down an octave," DiCaprio explained. "Even when you raise your voice it's like you got this frog in your throat. It's not necessarily being tired and it's not necessarily like being drunk. It's sort of like your body becomes jelly and all your bones and everything become completely relaxed. You just feel at peace. Supposedly. I don't know. I've never done it. Right?"
Jim Carroll was unaware of who Leonardo DiCaprio was at first. "When they first told me it was gonna be Leo, I didn't know who he was," Carroll told The Los Angeles Times. "If they'd said the kid from Growing Pains (1985), I would have known, because when I first saw that kid, I said, 'This kid has a lot of presence.' I said, 'That kid is very pretty. He's gonna do well.'"
Studio executives originally wanted the film to be set in Seattle. Director Scott Kalvert had read The Basketball Diaries (1995) when he was 15 years old and compared it to Catcher in the Rye. "Nobody really wanted to make the movie," Kalvert claimed. "Some wanted [the locale] changed to Seattle because Seattle was cool. Someone wanted to change it so Jim wasn't the one involved in drugs, and I had a specific take on it."