Systems including diphenylzinc, metallocene, and methylaluminoxane, at various combinations has been attempted, as initiating systems for homo- and copolymerization of styrene and various styrene related comonomers including : substituted styrenes, styrene derivatives, α-olefins, dienes and more recently cycohexenes including norbornene. The used metallocenes were those containing titanium, zirconium and for comparatives reasons hafnium. The metallocene efficiency towards syndiotactic polystyrene polymerization showed the order : titanocene > zirconocene > hafnocene. While the polymerization as well the copolymerization of Styrene with related to styrene compounds resulted to be much influenced by both electrical and steric hindrance effect. For styrene substituted derivative those group or element having I+ inductive effect depending its position at styrene’s its phenyl ring favours homopolymerization as well their copolymerization with styrene. The steric hindrance also showed a determinant influence on reactivity, so methyl and tert-butyl group, having a I+ effect, when at para-position improve activity and stereoregularity of their polymerization processes. But when placing at orto-position showed a very low capacity to polymerize. The present and previous results indicate that polymerization processes are initiated by monomer coordination to active metal species either of the binary metallocene-MAO or of the ternary Ph2Zn-metallocene-MAO.