Abstract: A thermally polymerized hydrogenated hydrocarbon resin and a novel process for hydrogenating a hydrocarbon resin. The resin is a copolymer of a feed which is a mixture of styrene and indene and derivatives thereof and cyclodiene monomers and dimers and optionally acyclic dienes. The process for hydrogenation of hydrocarbon resins is a process in which the resins are hydrogenated in the presence of an olefinic diluent which increases the hydrogenation reaction temperature to improve hydrogenation efficiency. The resin is useful in block copolymer and ethylene-unsaturated ester copolymer adhesive systems.