The effect of sulphur addition (2-58 ppm) during the catalytic partial oxidation (CPO) of methane was investigated on Rh-based honeycomb catalysts tested under self-sustained high temperature condition. Both steady state and transient operation of the CPO reactor were investigated particularly with regard to poisoning/regeneration cycles and low temperature light-off phase. The analysis of products distribution in the effluent and a heat balance demonstrates that sulphur reversibly adsorbed on Rh selectively inhibits the steam reforming (SR) reaction path to syngas production. The extent of SIR inhibition is greater when operating in air and diminishes at lower CH4/O-2 feed ratios. The poisoning effect has been shown to be independent from the type of sulphur bearing compound and only indirectly affected by the type of catalyst support (La2O3 or SiO2 stabilized alumina) through the value of Rh dispersion. (C) 2009 Elsevier B.V. All rights reserved.