Stone-fruit activated carbon (SAC) and modified versions containing acidic oxygen and basic nitrogen groups have been used to prepare palladium catalysts by wet impregnation. Carbon supports and catalysts are investigated by thermo-gravimetric analysis, TPD, oxygen chemisorption, TEM and XPS. The influence of the nature of the functional groups on the dispersion and oxidation state of palladium and its activity in hydrogen oxidation is investigated. Pd dispersion is found to increase with the basic strength of functional groups on the support. XPS reveals that introduction of amine groups in SAC results in an increased proportion of Pd-0, resistant to re-oxidation. Palladium catalysts supported on activated carbon modified by diethylamine groups are found to exhibit the highest metal dispersion and greatest activity in hydrogen oxidation. (c) 2007 Elsevier B.V. All rights reserved.