Ruthenium catalysts are widely used for selective hydrogenation of a carbonyl group in the vicinity of conjugated or isolated double bonds. The alpha,beta-unsaturated alcohols prepared in this way are compounds of great commercial importance. The effects of promoters, particle size and supports on such reactions are discussed. Ruthenium catalysts have also been applied in partial hydrogenation of aromatic compounds to the corresponding cycloalkenes. The effects of inorganic and organic modifiers on the course of the reactions together with a description of the action of catalysts prepared by the sol-gel method are given.