Sorption of LiCl, diffusion of Li+ ions, and diffusion of water have been studied as a function of the salt concentration in a synthesized cation-exchange resin bearing sulfonic acid groups, The Li+ diffusion shows a maximum in the salt concentration dependence reflecting on one side the enhanced diffusion due to screening of the fi?ted charges on the charged matrix and on the other hindered diffusion by shrinking of this matrix. A theoretical analysis is given in which the resin is visualized as being composed of spherical cells with the charged spheres placed in the centers. Also, the phenomenological approach of Glueckauf(4, 5) is applied. The spherical cell model gives a semi-quantitative prediction of the observed sorption and diffusion. The experimental results agree nicely with the semi-empirical power laws of Glueckauf.