Catalytic monoliths based on palladium supported on several inorganic oxides were prepared and characterized by XRD, HRTEM and NH3-TPD. The role of palladium and support in the dimethyl ether steam reforming reaction under a steam-to-carbon S/C=1.5 at 473-823 K was evaluated. The best catalytic performance in terms of hydrogen yield and low CH4 production was obtained over Pd/ZrO2 catalytic monolith. There is no apparent correlation between the hydrogen yield and acidity of the support and/or palladium dispersion, indicating that the interaction between Pd particles and the support may be a key factor in determining the catalytic performance. The reaction mechanism was studied by DRIFTS experiments. In addition to favor hydrogen recombination, Pd facilitates the formation of a methoxy intermediate species and its subsequent evolution into a reactive formate species. (C) 2010 Elsevier B.V. All rights reserved.