N-(2-Chlorobenzyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(16)H(12)ClNO(2), crystallizes in P2(1)/n with three crystallographically independent molecules in the asymmetric unit, which differ slightly in conformation, N-(2-bromo-4-methylphenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(16)H(12)BrNO(2), crystallizes in P2(1)/n with one molecule in the asymmetric unit and N-(2,3-dichlorophenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(15)H(9)Cl(2)NO(2), crystallizes in P2(1)/c with one molecule in the asymmetric unit. In all three structures, the heterocyclic rings adopt approximately planar conformations. The pyridine rings are orthogonal to the substituted phenyl rings. In all three structures, the crystal packing is stabilized by intermolecular C-H...O hydrogen bonds.