Dueck's total time in the super-G portion of the event was two minutes 18.2 seconds, putting him nearly a second ahead of Heath Calhoun, of the United States, and exactly two ahead of Roman Rubl of Austria.
The super combined is a two-part event including a slalom race and a super-G race.
Dueck, who is paralyzed from the waist down, sat in fifth after the slalom races, which were held on Tuesday. But those ahead of him struggled in the super-G. Japan's Taiki Morii, who'd been in third, crashed and did not finish the race, while Calhoun, Rubl and Germany's Thomas Nolte simply could not match Dueck's time.
The medal is Dueck's second of the 2014 Games and Canada's third gold.
He won the silver medal in the sitting downhill on March 8.