Pd/ZnO was modified using a co-precipitation method by introducing a third metal component: Mg, Al, Zr, Ce, La, Ru or a first row transition metal element. The catalytic performance of each combination in oxidative methanol reforming was evaluated at atmospheric pressure. The addition of Cr, Fe or Cu into Pd/ZnO increases the selectivity to hydrogen production by decreasing CO formation. Conversely, CO formation was markedly increased by the addition of Co, Ni and Mg. Modification with Al, Zr, La, Ce, Ru or Mn also increased CO formation to different extent. Pre-reduction of the samples at a higher temperature resulted in much less formation of CO in most cases, other than Co and Mg. This was confirmed, from XRD characterization of the spent catalysts, to be related to Pd-Zn alloy formation. (C) 2004 Elsevier B.V. All rights reserved.