The direct three-dimensional reconstruction of a polymer electrolyte fuel cell cathode catalyst layer from focused ion beam/scanning electron microscope (FIB/SEM) images is presented The carbon and pore distribution is shown and quantitatively analysed A new catalyst layer sample (Fumapem-F950/HiSpec13100) is sliced with FIB and a series of SEM images is taken The images are registered segmented and a three-dimensional stack is reconstructed The three-dimensional carbon and pore distribution is shown Based on the reconstruction the pore size distribution is evaluated The total porosity and the unconnected pores space is analysed The fully segmented 2D images are provided as supplemental material to this paper for future analysis and modeling work (C) 2010 Elsevier B V All rights reserved