Uniform-porous poly(dihydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(DHPM-co-EDM) particles were synthesized as an alternative packing material for reversed phase chromatography. In the synthesis, poly(glycidyl methacrylate-ethylene dimethacrylate), poly(GMA-co-EDM) particles were obtained by a multi-stage swelling and polymerization protocol, the so called '' modified seeded polymerization ''. For this purpose, 2.4 mu m polystyrene seed particles were first swollen by dibutyl phthalate (DBP) and then by a monomer mixture including glycidyl methacrylate and ethylene dimethacrylate. The repolymerization of monomer phase in the swollen seed particles provided porous uniform particles approximately 7 mu m in size. Poly(DHPM-co-EDM) particles were obtained by the acid hydrolysis of the particles synthesized with different GMA feed concentrations. These particles were used as column-packing material in the reversed phase separation of alkylbenzenes. The retention factor-acetonitrile concentration diagrams clearly showed that the polarity of packing material could be controlled by changing the GMA feed concentration in the '' modified seeded polymerization ''. The packing materials with more hydrophobic character (i.e., poly(EDM) and poly(DHPM-co-EDM) particles produced with the GMA feed concentrations up to 20%) exhibited better chromatographic performance in the reversed phase mode.