New Nickel (II) catalytic systems based on N,O chelate ligands, activated by methylaluminoxane, have been checked in the homopolymerization of methyl methacrylate (MMA) and its copolymerization with ethylene. In particular, the bis(8-hydroxy-5-nitro-quinolate)nickel(II)/methylaluminoxane system as well as the catalysts obtained by oxidative addition of either 8-hydroxy-5-nitro-quinoline or 8-hydroxy-5,7-dinitro-quinoline or 4-nitro-2-(p-nitrobenzylideneamino)-phenol to Ni(cod)(2), subsequently activated by methylaluminoxane, have been employed. The influence of the reaction parameters on the catalytic activity and the characteristics of the resulting polymers has been investigated. All the obtained poly(methyl methacrylate) samples display a largely prevailing syndiotacticity degree, high molecular weights and a rather large polydispersity. The catalytic systems obtained through the oxidative procedure are able also to give copolymers of MMA with ethylene producing highly linear polyethylenes containing a low amount (1.5-2 mol %) of MMA counits, thus affording materials with improved surface properties. (c) 2005 Wiley Periodicals, Inc.