Decoration with transition metal catalysts has been reported to enhance H-2 storage capacity of carbon materials at ambient temperature. Furthermore, it has been proposed that surface oxygen groups may improve the process. In this study, a carbon molecular sieve was subjected to controlled oxidation and consequent doping with Pd nanoparticles. The H2 sorption performance of the pristine and oxidized, undoped and doped materials was examined at 298 K up to 20 bar. It was found that the non-oxidized carbon-Pd composite did not show any spillover based sorption increase. On the other hand the oxidized samples reveal a slight enhancement that could be attributed to a weak chemisorption process initiated by the so-called "spillover" effect. Overall, the contribution of spillover to the total hydrogen storage capacity of this system (under the conditions studied) was not found to be of great significance. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.