Poly(cyclic conjugated diene) polymers are prepared by polymerizing a cyclic conjugated diene monomer or cyclic conjugated diene monomer and a double bond-containing monomer using a transition metal catalyst, preferably a Ni-based catalyst, in a non-polar solvent containing a basic compound or an aromatic halide solvent. The poly(cyclic conjugated diene) polymer may then be subsequently modified by reaction of at least one of the double bonds of the polymer with a modifying substance, for example hydrogen.