The structural heterogeneity of synthetic phosphoric acid activated carbons has been analyzed using pore-size distributions (PSDs) obtained from nitrogen at - 196 degreesC and carbon dioxide at 0 degreesC isotherms. PSDs where obtained by the BET-Kelvin method. It is shown that the BET-Kelvin method is in good agreement with DFT and provides a fast means for assessment of the porous structure of adsorbents. PSDs obtained by the BET-Kelvin method using different adsorbates give results consistent with each other. Due to the restricted pressure range for carbon dioxide adsorption isotherm the PSD gives information only about pores in the micropore range. The agreement between different methods is better for small micropores. (C) 2002 Elsevier Science B.V. All rights reserved.