In the present work we report the results of the Polymerization of styrene using diphenylzinc-butanone, Ph2Zn-MeCOEt. Our results indicate that these systems induce the polymerization of styrene reaching a larger conversion when the molar ratio MeCOEt/Ph2Zn = 1,0. According to size exclusion chromatography, SEC, studies of the polystyrene obtained using the Ph2Zn-MeCOEt showed unimodal curves and have molecular weight distribution narrower than those obtained using the Ph2Zn-H2O system, suggesting a more simple reaction system.