...semi-finals on Tuesday.
Serbia's Jankovic, seeded fourth, showed signs of nerves at times but relied on her ferocious backhand and tremendous court speed.
The 18-year-old Vaidisova, who burst into the limelight by reaching the semi-finals here last year and was seeded sixth, survived four match points before bowing out by netting a forehand.
Jankovic, 22, who established herself as a top contender by winning three titles this year to break into the top five, will meet defending champion Justine Henin or Serena Williams for a place in the final.