Using inverse exclusion chromatography, the porous structure of four polymeric stationary phases has been investigated. Three of the copolymers were characterized by a high degree of crosslinking because they were synthesized from I',,vo tetrafunctional monomers. The fourth copolymerwas obtained from styrene (bifunctional monomer) and divinylbenzene (tetrafunctional monomer) and has a significantly smaller degree of crosshnking.To determine the pore size distribution of the copolymers, toluene, alkylphenones, phthalates, and polyslyrene standards were used as probes. Additionally changes of the volume of the copolymers when changing from water to tetrahydrofuran were determined. The results show that more stable porous structures were obtained from tetrafunctional monomers. All polymeric stationary phases have micropores in their internal structure but their contributions are different.