Pd and Pd-Sn supported on SiO2 and active carbon were prepared and tested as catalysts in the hydrogenation of maleic anhydride. Particularly Pd-Sn/SiO2 was active and selective in the hydrogenation of maleic anhydride to gamma-butyrolactone, and showed a resistance to the deactivation. The results of XPS and CO adsorption evidenced that the catalytic performance of Pd-Sn/SiO2 was related to the modification of electronic configuration of Pd due to the effective interaction between Pd and Sn. (C) 2003 Elsevier B.V. All rights reserved.