The properties of Ru/Al2O3 catalysts prepared using RuCl3 as precursor and subjected to different treatments after impregnation, were studied using different techniques: XPS, FTIR, hydrogen chemisorption and thermal programmed reduction. Differences in the Ru species (Ru-0, ruthenium oxides and ruthenium oxychloride), metal dispersion and chlorine content in the catalysts as well as in their catalytic activity and selectivity during benzene selective hydrogenation to cyclohexene, were found according to the preparation procedure used. (C) 2003 Elsevier Science B.V. All rights reserved.