Paerson edged out the other two skiers in combined downhill and slalom runs.
Vonn, who won the downhill portion and placed 16th in the slalom, increased her overall World Cup lead to 157 points over Riesch, whose runner-up finish moved her ahead of Austrian Nicole Hosp in the standings.
"The slalom was really tough because it was warm and the snow turned to slush," said Vonn, of Vail, Colo. "I went a little too straight going into the flat section and I lost all of my speed. But, I'm really happy with third-place."
Paerson's win was her third of the season.