Parini, the World Cup leader, roared down a hard fast course in 2 minutes, 18.51 seconds to catch American Sondra Van Ert on the second run.
Fellow Italian Lidia Trettel finished second in 2:19.10 while Van Ert, the defending champion, faded to third at 2:19.24.
Parini said her first major title made up for Nagano, where the 26-year-old broke into tears after a disastrous first run led to a 13th-place finish.
“This medal is for me — I’ve worked so hard,” Parini said.
Van Ert was initially awarded second place, but International Ski Federation officials revised Trettel’s time a half hour after the race after discovering a timing malfunction.
Van Ert, leader after the first heat, seemed to have the race won when she still led by almost a half-second midway through her second run.
But she slowed on the lower portion of the course to fall back to third.
“My coaches said I lost a second and a half there,” Van Ert, 34, of Ketchum, Idaho said. “I have no idea why. Maybe I thought, `Hey, you’ve survived the toughest part of the course’ and let down.”
Both the Olympic gold medalist, France’s Karine Ruby, and silver medalist Heidi Renoth of Germany took themselves out of contention with poor first runs.
Ruby, spinning out on her first run, finished 13th and Renoth 43rd.
Van Ert, who once finished 11th in an World Cup Alpine downhill race before switching boards, now has two bronzes and a gold in the three snowboard world championships.
“I’d rather have a gold today, but I’ll take it — that’s something,” she said.
Rosie Fletcher of Girdwood, Alaska was third after the first run, but crashed near the finish line to finish 19th.
Copyright 1998 The Associated Press.