Dimethyl ether (DME) steam reforming for hydrogen production has been studied on a bifunctional catalyst prepared by the (wet) physical mixing (at 50 wt%) of a metallic function of CuO-ZnO-Al2O3 (Cu/Zn/Al atomic ratio = 4.5:4.5:1.0, prepared by co-precipitation) and an acidic function of HZSM-5 zeolite modified by alkaline treatments of different severity. The runs have been carried out in a fluidized bed reactor. The results obtained by using treated HZSM-5 zeolites and gamma-Al2O3 as acid functions have been compared. The alkaline treatment affects both the acid properties of the zeolite (attenuating total acidity and acid strength) and its porous structure (increasing the mesoporous surface and decreasing the microporous volume and BET surface area). The attenuation in acidity hinders the formation of undesired hydrocarbons from oxygenates (methanol + DME). Consequently, alkaline treatment (with 0.2-0.4 M NaOH solutions for 300 min) is suitable for improving the kinetic performance of the bifunctional catalyst, as it provides high selectivity and a high yield of H-2 at 300 degrees C without hydrocarbon formation, as well as minimizing CO formation and avoiding deactivation by Cu sintering. The catalyst is stable, and its kinetic performance remains constant throughout long runs. (c) 2012 Elsevier B.V. All rights reserved.