We set up and validated a volumetric method to quantify the amount of hydrogen "delivered" after saturation of a solid material as adsorber at different pressures (up to 100 kg(f)/cm(2)) and temperatures (down to 77 K). This is the practically most relevant datum to quantify the effectiveness of an adsorbent for the present application. A complementary dynamic method has been also developed to take into account the reversibility of adsorption and to assess in at least a semi-quantitative way the strength of interaction between H-2 and the adsorbent. The method has been applied to compare the hydrogen storage capacity of some significant different carbon-based materials (two active carbons and one graphite), as supplied or after thermal treatments under oxidising or reducing conditions. The best results, ca. 7 wt% H-2 "delivered", were achieved after saturation at 77 K, 20 kg(f)/cm(2) with an active carbon with ca. 3000 m(2)/g of apparent specific surface area. The thermal treatments, almost always inducing a drop in surface area, showed effective only for saturation at 273 K, in particular the oxidising procedure. This was correlated to the formation of surface oxidised species, likely carboxylic groups, which improved the interaction strength between H-2 and the adsorbent. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.