It was found that the main products of gamma-radiolysis (Co-60) of liquid 5-vinyl-2-norbornene (VNB) and 5-ethylidene-2-norbornene (ENB) and their solutions in cyclohexane and benzene are polymers. The structure of these polymers was determined by means of IR spectroscopy. It was shown that the polymerization of individual VNB engages both C=C bonds of the diene and involves norbornene ring opening. In the case of individual ENB, only one, exo-cyclic, C=C bond participates in polymerization retaining the norbornene ring intact. In cyclohexane solutions, mixtures of VNB and ENB polymers of the same type are formed, which are predominantly composed of saturated compounds. It was found that polymerization during gamma-irradiation of VNB solution in benzene proceeds via the addition of benzene radicals to one, endo-cyclic, C=C bond of VNB. The produced 2-vinylnorbornane moiety of this polymer was identified via comparison of its IR spectrum with that of unirradiated 2-vinylnorbornane.