The activity behavior of steam reforming of methanol was studied over Cu/CeO2/gamma-Al2O3 catalysts with different compositions in a parallelized 10-channel microreactor. It was found that the catalytic performance is strongly influenced by the catalyst compositions, i.e. copper and ceria loading. Cu/CeO2/gamma-Al2O3 catalyst thin films before and after use in the microreactor were extensively investigated by means of surface analysis techniques like X-ray photoetectron spectroscopy, energy dispersive analysis of X-rays, and thermal desorption spectrometry. The parallel screening result is tentatively discussed on the basis of the surface analysis characterization results and previous proposals. The rationalized correlation of the catalytic activity dependence with the characteristics is in line with a reaction mechanism, which supposes that the copper/ceria boundary is the active site for steam reforming of methanol and the oxygen reverse spillover from ceria to copper is involved in the catalysis cycle. (C) 2004 Elsevier B.V. All rights reserved.