The ethanol steam reforming (ESR) is studied in a parallel plate reactor with square channels of 500-2000 mu m and washcoated with Pd-based catalyst. The endothermic process is co- or countercurrently heated by means of a flue gas stream flowing through contiguous channels. Two contiguous square channels, assumed as representative of the whole reactor behavior, are simulated using both 1D pseudohomogeneous and heterogeneous models for comparison purposes. The influence of the main operating variables, flow configuration and design parameters on the performance of the reformer has been analyzed. The reactor performance is mainly controlled by the heat supply from the flue gas to the process stream. For low inlet temperatures of the ethanol + water feed, the countercurrent flow configuration allows improved heat recuperation and the reactor shows a higher performance. Conversely, when the feed is pre-heated upstream the reactor, the cocurrent scheme appears preferable due to a more favorable axial profile of heat transferred. The channel width has a strong influence on the hydrogen production rate and the residual methane slips when cocurrent operation is selected. For the countercurrent scheme, a more robust design is achieved in terms of ethanol conversion and hydrogen yield for variations in the feed temperature. Moreover, the channel dimension losses influence provided enough small channels are considered. The heat conduction phenomenon through the solid metal wall was studied varying the wall thickness; diminished reactor performance for thicker walls was observed due to a drop in the heat duty. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.