Abstract Catalytic hydrogenation of variously substituted 1-arylisoquinolin-3 (2H)-ones 1 gave, depending on the substituents, 5, 6, 7, 8-tetrahydroisoquinolin-3 (2H)-ones (2) and/or the corresponding 1, 4-dihydro derivatives 3. Saturation of the compounds fused with benzene ring furnished as the main products the 9, 10-dihydro-(4 and 5) and 5, 6- dihydroisoquinolin-3 (2H)-ones (6) in the case of benzo [f] and benzo [h] anellation, ...