Ln-dosed Ag/SiO 2 (Ln = Eu and Yb) bimetallic catalysts were prepared by the reaction of SiO 2-supported Ag (Ag/SiO 2) with a solution of lanthanide metals dissolved in liquid ammonia. The catalytic properties were extensively studied by the hydrogenation of ethene and buta-1,3-diene. The hydrogenation behaviors varied markedly with the loading amounts of silver in the catalyst precursors (7, 20, 30 and 50 wt.% Ag/SiO 2) and the lanthanide content in the bimetallic LnAg catalysts. The activity increased with the loading of silver in the precursor and the lanthanide content. The catalytic nature of the bimetallic Ln-Ag surface drastically changed between the low and high lanthanide content. Ln-Ag/SiO 2 exhibited changes in reactivity for ethene and buta-1,3-diene; thus in the region of low lanthanide content in LnAg the order of decreasing activity for the hydrogenation was obtained as buta-1,3-diene and ethene, and reversely for higher contents. For the hydrogenation of buta-1,3-diene, but-l-ene and cis-but-2-ene were primarily produced in the region of low lanthanide content (0 < Yb/Ag < 0.15), while trans-but-2-ene was major for higher contents (0.15 < Yb/Ag).