Previous research has shown that hydrogen production performance of a PEM methanol electrolyzer was largely improved with a porous flow field made of sintered spherical metal powder compared with a conventional groove type flow field. In this study, we experimentally investigated the effect of the change in grain diameter and material of the porous metal flow field on hydrogen production performance in a PEM methanol electrolyzer cell. The experimental results indicated that the hydrogen production performance of the electrolyzer cell was improved by reducing the grain diameter. This could be mainly attributed to the lower interfacial contact resistance by reducing the grain diameter of the porous metal flow field. For investigating the influence of material, cell performances with a stainless steel and a nickel base alloy were compared. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.