Atom transfer polymerization of styrene using N-aryl-substituted pyridinimines and N,N'-diaryl-substituted diimines as N,N'-ligands in the presence of Cu(I)Br and l-phenylethyl bromide has been investigated and compared with the analogous 2,2'-bipyridine system. A molar mass increase which is consistent for a controlled polymerization with a target molar mass of 10000 g.mol(-1) is observed with the 2,2'-bipyridine (1) and the pyridinimine (2a) systems. The polymerization of styrene with the N,N'-diimine system (3) is much less controlled, yielding polymers with higher molar masses than expected.