In this theoretical work the effects of the parameters governing the hydrogen permeation through the dense palladium membranes on the membrane reactor performances are studied. The model for the methane steam reforming was used as test reaction system and the effects of the parameters of the Richardson equation (n, P-0 and E-a), on the reactor performances were studied. The effect of the hydrogen flux pressure and temperature dependence factors on the methane conversion and on the hydrogen recovery for both the co-current and counter-current modes are reported and discussed. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.