When the producers of "Gia" (HBO, January 31, 9 p.m.) cast 22-year-old Angelina Jolie as the heroin-addicted, lesbian '80s supermodel Gia Carangi,

they knew the young actress could capture both the fashion star’s beauty and her winsome vulnerability.

Jolie, whose past credits include “Hackers” and “Playing God,” admits to a certain identification with the character, particularly with Gia’s fiery spirit. (Among other things, Gia, who died of AIDS in 1986, was known to pull a switchblade on people who disagreed with her.) But no one foresaw how closely Jolie, the daughter of actor Jon Voight, would connect with the late model’s problems with self-esteem. “Oh, God, I struggle with low self-esteem all the time!” says Jolie. “I think everyone does. I have so much wrong with me, it’s unbelievable!”

According to Jolie, there are even more similarities between her own life and the controversial and emotionally draining role. Like the character she plays, Jolie comes from a broken home, was at one time fascinated by heroin, and makes her living in a profession that prizes beauty — often above all else.

“I’ve definitely needed to learn the lessons Gia needed to learn,” says Jolie. “Especially feeling that the physical is more important than anything else, or that you’re only as smart and good as somebody thinks you are. It’s been really important for me to look at myself in the mirror, and realize that I can’t let myself go down like she did.”

The actress admits there were times during the production when the lines began to blur. “I’d think, ‘Oh, God, I have to be perfect today. I can’t get a pimple! I can’t have dark circles. And I’m gaining weight!’ And I thought, ‘Well, that’s exactly how Gia must have felt.'”

While the production has a clear anti-heroin theme, Jolie hopes viewers will take away another message too: “I want them to identify with Gia and see her as being just a regular girl. No matter how together or perfect some people may appear, they have their share of pain and a deep-down need for love — the same as everyone else.”