Even traces of CO in the hydrogen-rich gas fed to PEMFC can poison the platinum anode and dramatically decrease the cell power output. Micro-chemical technology (MCT) is a new direction of chemical engineering originated in the early 1990s. The application of MCT can greatly improve the efficiency of systems and diminish their volumes and weights. The novel reaction conditions such as the very low residence times in micro-structured reactors create the need for adopting or even improving conventional catalyst technology according to the requirements of this new application. On top of the improved heat and mass transfer, micro-structured reactors allow for a better temperature control of the reaction. In the present paper, a screening of powder Rh-based catalysts, was carried out for CO preferential oxidation reaction, and then the more promising catalyst was deposed and tested in a microchannel reactor. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.