Chlorobenzene hydrodechlorination in liquid phase has been studied. Chlorine released during the reaction inhibits conversion in large metallic particles. It was found comparing the behavior of Pd/SiO2, Pd/Al2O3 and Pd/C catalysts that the support plays the role of a chlorine trap. The activity for Pt, Rh and Pd at similar dispersions corresponds to the chlorine adsorption affinity of the metals.