The reaction of benzene, naphthalene and anthracene with dihydrogen under a pressure of 3 and 20 bar at 80 degreesC in the presence of [RuH2(H-2)(2)(PCy3)(2)] (1) leads to cyclohexane, tetralin and a mixture of 1,2,3,4-tetrahydroanthracene (4H-An) and 1,2,3,4,5,6,7,8-octahydroanthracene (8H-An), respectively. Surprisingly, the increase of dihydrogen pressure lowers the yield of hydrogenation products. Product 1 may be used directly as a catalyst precursor or may be prepared in situ from [RuH{(eta (3)-C6H8)PCy2} {eta (2)-C6H9)PCy2}] (2) under dihydrogen at room temperature. A number of functionalized arenes (toluene, chlorobenzene, durene) as well as tetralin, phenanthrene and 9,10-dihydroanthracene are not reduced under 3 bar of dihydrogen. The reaction of 1 with arenes, either in neat benzene or in cyclohexane in the case of naphthalene and tetralin at 80 degreesC leads to the formation of respectively, eta (6)-bound benzene (3), naphthalene (4) and tetralin (5) complexes that are also present in very small quantities in the final catalytic mixtures. Reaction of I with anthracene at room temperature yields the complex [Ru(eta (4)-C14H10)(PCy)(2)] (6) containing an eta (4)-bound anthracene. Product 6 shows a catalytic activity for anthracene hydrogenation and can be regarded as an intermediate in the catalytic cycle.