The relationship of water uptake and pore volume has been investigated for porous styrene-divinylbenzene (St-DVB) copolymers prepared in the presence of different inert diluents. It was found that the copolymers prepared in some conditions significantly increased their volume on taking up the water (swelling), and thus the use of water to measure the pore volume of porous St-DVB copolymers could hardly be recommended because the water uptake measurement does not always give a true value of the pore volume in dry state. (C) 2000 Elsevier Science B.V. All rights reserved.