The preparation and characteristics of poly(divinylbenzene-co-ethylvinylbenzene), including the resin Amberlite XAD-4 available from Rohm and Haas Company, were studied. The monomer and vinylbenzene group content, surface area, and pore size of lab-made resins were compared to those of the commercial resin. Compared to lab-made resins, we have found that Amberlite XAD-4 has a much higher surface area and porosity, making it an ideal matrix for preparing functional resins by modification of pendant vinylbenzene groups. The degree of functionalization of vinylbenzene groups for XAD-4 ranged from 29 to 41%, approximately one-third of repeat units having a pendant vinyl group.