Jankovic, the 19th seed, smashed the Russian 6-2, 6-1. In the first Grand Slam semifinal of her career, Jankovic will play either 10th-seeded American Lindsay Davenport or second-seeded Belgian Justine Henin-Hardenne, matched against each other in Tuesday night's quarter-final.
A Serbian who lives and trains in Florida, Jankovic has moved up through the majors this year to the second round in the Australian Open, the third round at the French Open and the fourth at Wimbledon. In her previous U.S. Open match, she defeated sixth-seeded Svetlana Kuznetsova of Russia.
Dementieva played sluggishly, never holding serve and committing five double faults and 39 unforced errors.