The scope and limitations of RuCl2(3-bromopyridine)(2)(H(2)IMes)(CHPh) (H2IMeS = N,N-dimesityl-4,5-dihydroimidazol-2-ylidene) as the initiator for living ring opening metathesis polymerization (ROMP) of functionalized norbornenes are evaluated. While norbornene derivatives exhibiting different propagation rate constants could be successfully employed in the preparation of block copolymers irrespective of their sequence of addition, the usage of cyano functionalised monomers is restricted. This phenomenon could be rationalized by a coordination of the cyano group to the ruthenium centre. (c) 2006 Elsevier B.V. All rights reserved.