A series of anthracene and acridine derivatives were hydrogenated under mild reaction conditions (80° C, 3 bar of H2) using the bis (dihydrogen) complex [RuH2 (η2-H2) 2 {P (C6H11) 3} 2](1) as a catalyst precursor. The influence of a methyl substituent on the substrate was studied. In all our systems, hydrogenation was only observed at the external rings leading to the corresponding 4H-or 8H-derivatives of anthracene and acridine. ...