The kinetic dependences of sorption (a) and deformation (xi) measured simultaneously in samples of coals of different ranks have been obtained. The experimental xi(a) dependences have been used to analyze the relationship between sorption and swelling. These dependences have proved to be linear. This allows us to introduce a parameter characterizing the normalized sorption. A model describing the relationship between the new parameter and the sorbate density is proposed. Analysis of the dependence of the parameter on the coal rank has yielded two groups of xi(a) dependences, which indicates that coals of different ranks differ from one another in the mechanisms of swelling. The adsorbed substance density has been estimated in both groups. The density estimates are plausible for high-rank coals but not for low-rank ones. (C) 2008 Elsevier Ltd. All rights reserved.