Norbornene-ended polybutadiene (PBu) macromonomers have been prepared via two different routes: a-norbornenyl-polybutadiene was derived from a norbornene-containing carbanionic initiator, whereas w-norbornenyl samples were obtained through deactivation of living polybutadienyl anions by a norbor-nene-based deactivator. Out of four alkylidene complexes tried, the molybdenum alkylidene complex that contains two alkoxide ligands was found to be the most suitable initiator for the ring-opening metathesis polymerization of these macromonomers.