The gold went to the reigning champions, Aliona Savchenko and Robin Szolkowy from Germany, with China's Zhang Dan and Zhang Hao claiming the silver.
Smirnov and Kawaguchi were lying in second place after the short program, but were unable to hold on during the free skate late on Wednesday.
Japanese-born Kawaguchi has been skating with Smirnov since early 2006. She and Smirnov are the 2008, 2009 Russian Champions and the 2009 European silver medalists.
Kawaguchi was officially granted permission by the Japan Skating Federation (JSF) to represent Russia at major international events last month. The athlete has been living in Russia's second largest city of St. Petersburg since 2002, where she graduated from the St. Petersburg University, majoring in international politics.
