The hydrogenation of petroleum resins (PRs) in the presence of commercial NVS-A, GO-15K, AGKD-400, and AKM nickel-tungsten, cobalt-molybdenum, and nickel-molybdenum sulfide catalysts and sulfided palladium MA-15 has been studied. Features of changes in the average molecular mass (M) of the PRs in the presence and absence of sulfur compounds in the reaction medium have been determined. The highest degree of hydrogenation is achieved in dilute PR solutions with a concentration of 10-20%; an increase in the process temperature and pressure leads to an intensification of the polymer chain degradation reactions. Swelling of the polymer globules in "good" solvents (benzene, toluene) makes the polymer chains more accessible to the active sites of the catalyst and thereby leads to an intensification of both the hydrogenation and thermal degradation reactions. The process run without any solvent does not provide a sufficient degree of hydrogenation of aromatic moieties owing to the high viscosity of the reaction mass and the resulting high diffusion restrictions.