Polystyrene macromonomers, fitted with a norbornenyl unsaturation in cr position, have been obtained from a norbornene based carbanionic initiator that has been purposely designed to this end. The advantages of this synthetic scheme over that based on the deactivation of living PS chains are emphasized. One of the macromonomers prepared has been subsequently polymerized by ring-opening metathesis, using a Schrock complex as initiator. The characterization of the resulting polymacromonomers showed that the metathesis process occurred under ''living'' conditions.