Fifth-seed Dementieva cruised to a 6-2 6-1 victory over Israel's Shahar Peer to reach the last eight for the second time in three years. Peer had defeated Russia's Dinara Safina in the previous round.
Nadia Petrova, seeded 21st, overpowered compatriot Alla Kudryavtseva 6-1, 6-4. Kudryavtseva, ranked 154 in the world, had been a relative unknown before her shock victory over Maria Sharapova in the second round.
Of the other three Russian women in the fourth round, fourth-seed Svetlana Kuznetsova was defeated by Poland's Agnieszka Radwanska, Alisa Kleybanova lost to Venus Williams of the U.S., and eighth-seed Anna Chakvetadze was beaten by the Czech Republic's Nicole Vaidisova.
In the men's singles, Russia's Marat Safin is currently playing Switzerland's Stanislas Wawrinka for a place in the quarter finals. Earlier in the day the other Russian competing in the fourth round, Mikhail Youzhny, lost 3-6, 3-6, 1-6 to Spain's Rafael Nadal, the number two seed.