The copolymerization of styrene with p-methylstyrene has been tested using combined diphenylzinc-additive initiator systems, including diphenylzinc, Ph2Zn, a metallocene: cyclopentadienyltitanium trichloride, CpTiCl3, and methylalumoxane, MAO, as well as the binary CpTiCl3-MAO initiator system. Both combined initiator systems were able to induce S/p-MeS copolymerization and the corresponding homopolymerizations. Conversion to copolymer increases with an increase of p-MeS in the initial feed, while p-MeS homopolymerization led to greater conversion than that of S. From the copolymers obtained using these initiator systems only those produced from S/p-MeS = 95/5 (mol/mol) in the feed showed to be crystalline, with Tm values lower than that of pure s-PS, making them easier to process