Poly(N,N-dimethyl acylamide) re sins, cross-linked up to 8 mol % with methylenebisacrylamide, have been investigated in the swollen state (dichloromethane, DCM, and tetrahydrofuran, THF) by means of inverse steric exclusion chromatography (ISEC) and electron spin resonance spectroscopy (ESR). Their behavior has been evaluated on the basis of a physicochemical model, which was previously developed to describe the behavior of the same materials in water. This model is based on the assumption that the swollen resins can be depicted as concentrated viscous polymer solutions. In DCM, this hypothesis still holds for the relatively lightly cross-linked swollen gels, while it is not acceptable when the crosslinking degree is higher than 4 mol %. When THF is used as the liquid medium; the investigated resins do not fully swell, and the spin probe employed for the ESR measurements is adsorbed from the liquid phase onto the polymer chains. Therefore, the characterization of these polymers swollen in THF did not give unambiguous results. The same ISEC-ESR combined approach has been exploited to study the swelling behavior of several sequential interpenetrating organometallic polymer networks. These materials were obtained upon dispersion of different amounts of an organometallic, cross-linked copolymer-co(vinylferrocene/N,N-dimethylacrylamide/methylenebisacrylamide)-inside a poly(N,N-dimethylacrylamide) resin, cross-linked with methylenebisacrylamide (4 mol %). Th, introduction of the "guest" copolymer into the tridimensional network of the resin has been found to increase the swelling volume of the "host" matrix.