A study has been carried out on the effect of combining the metallic (CuO-ZnO-Al2O3) and acid (HZSM-5 zeolite treated with NaOH) functions, and of their mass ratio, on the kinetic performance in the steam reforming of dimethyl ether (SRD). The runs have been conducted in a fluidized bed reactor in the 225-325 degrees C range, and the reaction indices (dimethyl ether and methanol conversions, and H-2 and CO yields) have been explained based on the physico-chemical properties of the catalyst. A suitable synergism between dimethyl ether hydrolysis and methanol reforming steps requires striking a balance between acidity and the number and dispersion of metal sites, as happens in the catalyst prepared by wet physical mixing with a mass ratio of 1:1 between the metallic function and the acid one. This catalyst allows obtaining high values of dimethyl ether conversion and H2 yield in the 275-300 degrees C range by minimizing the CO formation rate and deactivation by coke. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.