In this theoretical work the performance of different membrane reactor concepts, both fluidized bed and packed bed membrane reactors, has been compared for ultra-pure hydrogen production via methane reforming. Using detailed theoretical models, the required membrane area to reach a given conversion and the prevailing temperature profiles have been compared. The extent of mass and heat transfer limitations in the different reactors has been evaluated, and strategies to decrease (or avoid) these limitations have been proposed for the fluidized bed membrane reactor concept. The results show that the packed bed membrane reactor requires in some conditions double membrane area with respect to the fluidized bed membrane reactor. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.