The behavior of strong acid cation exchangers in nonaqueous solvents and in aqueous-organic solvent mixtures has been extensively investigated during the past decades. 1–9 Modeling of multicomponent sorption equilibria and of diffusion of liquids in a swollen cross-linked polymer network plays a key role in understanding ion exchange resin catalysis and membrane separation processes. It is well known that the solvent sorption equilibria and resin swelling kinetics are influenced by the nature of the functional group, the counterion, and the polymer matrix, as well as the cross-link density of the resin. The purpose of the present work is to investigate the role of the elastic properties of the resin on these two phenomena in solvent mixtures. We also demonstrate the use of a thermodynamic modeling approach in describing sorption and swelling equilibria as well as swelling kinetics of ion exchange resins. The essence of this approach is that the elastic properties of the resin are explicitly taken into account.