The method of neutron diffraction and isotopic substitution was applied to aqueous (D2O) poly(styrene sulfonate) ion exchange resins with Ni2+ and Li+ as counterions. In q-space, a significant effect of the presence of the polyion is observed on the structure of the surroundings of the ions, in particular for Li+. In its real space representation, the data indicate the possibility of direct contacts between ions and charged groups on the polyionic network.