A multiscale methodology is presented to analyze the transport and reaction processes in the catalyst coating of a microstructured reformer and to elucidate the effect of catalyst morphology on transport limitations and the reformer performance. This analysis includes three-dimensional simulations of methane steam reforming at both reactor level (macroscale) and catalyst microstructure level (microscale). Hypothetical catalyst microstructures are generated using an in-house particle packing code. Based on the generated structures, the effective transport properties of the porous catalyst and the average reaction rates in the microstructure are determined to be applied in the pseudohomogeneous model used in the macroscale simulation. Parametric study is done to demonstrate the significant effect of the catalyst intraparticle and interparticle porosity as well as the particle size on the reaction effectiveness factor and methane conversion. This study shows that an optimal catalyst coating has a decreasing porosity along the reformer length based on the difference in the degree of diffusion limitation. (c) 2014 American Institute of Chemical Engineers AIChE J, 60: 2263-2274, 2014