Kvitova, the No. 6 seed at the Dubai Duty Free Tennis Championships, took out Radwanska 6-2, 6-4 with five breaks in the match.
Kvitova went 4-for-4 in break opportunities in the first set, allowing Radwanska just nine points in four service games. Radwanska had more success serving in the second set but Kvitova posted the only break of the set and advanced.
The loss by Radwanska, ranked No. 4 in the world, means the tournament lost its top four seeds. No. 1-seeded Victoria Azarenka and second seeded -- but No. 1-ranked -- Serena Williams each withdrew because of injury and fourth-seeded Angelique Kerber lost a second-round match.
That leaves No. 5-seeded Sara Errani as the highest seed in the draw. Errani moved to the semifinals with a 6-4, 0-6, 6-3 win over Nadia Petrova. The second set was so lopsided that Petrova won more points (105-104) on the day but Errani had five breaks total in the first and third sets.
Errani plays Vinci in one semifinal Friday. Errani is 4-2, with a four-match winning streak, lifetime against Vinci. Kvitova and Wozniacki, the other semifinal pairing, have split their six career matches.