Dementieva, No. 10 in the world and seeded seventh in Tokyo, got past fifth-seeded Francesca Schiavone 6-4, 7-5 in semifinal play and Wozniacki, No. 2 in the world and the top seed for the Pan Pacific Open, edged eighth-seeded Victoria Azarenka 6-2, 6-7 (3-7), 6-4 in advancing.
Wozniacki's semifinal lasted nearly 3 hours. She broke Azarenka's serve 10 times in 15 games and overcame seven breaks of her own. Neither player won most of the points on serve.
Wozniacki ran off to a 5-0 lead in the third set only to have Azarenka rally in a string in which she won 16 or 19 points. But Wozniacki finished the match by serving out at love.
Dementieva needed nearly 2 hours to advance over Schiavone. She had six service breaks -- three in each set -- which overcame her own four breaks and seven double faults.
Saturday's title match will mark the seventh career meeting between Wozniacki and Dementieva. Both have won three times, with Wozniacki's tight, three-set win in Connecticut this year the latest pairing of the two.
The Pan Pacific Open title is worth $350,000 to the winner and the runner-up will receive $175,000. Schiavone and Azarenka won $87,500 as semifinalists.