(CNN) -- Fourth seed Elena Dementieva, the highest-ranked player left in the women's draw in the China Open in Beijing has been beaten in straight sets by Agnieszka Radwanska.
12th seed Radwanska is through to the Beijing semis after defeating Elena Dementieva in straight sets.
Radwanska, seeded 12th, had only reached the last eight after surviving a scare against Spain's Maria Jose Martinez Sanchez -- but she broke six times as the Russian's sometimes brittle serve failed her once again, going down 7-5 6-3.
Pole Radwanska will now face France's Marion Bartoli, who came from behind to beat another Russian, Vera Zvonareva, 3-6 7-5 6-2.
The other semifinal will be an all-Russian affair between Nadia Petrova and French Open champion Svetlana Kuznetsova.
Petrova, seeded 13th, came from a set down against home favorite Peng Shuai to win a two-hour 40-minute battle.
Peng, who beat Jelena Jankovic and Maria Sharapova earlier in the tournament, broke only once in the match but took the opener on a tie-break before Petrova rallied to a 6-7 6-3 6-2 win.
She will face sixth seed Kuznetsova, who won the all-Russian last-eight clash 6-3 6-3 against Anastasia Pavlyuchenkova.