The crystal structures of two compounds-3-benzoyl-4-hydroxy-4-phenyl-(N-methyl)piperidine(I) [orthorhombic crystals, space group P2(1)2(1)2(1), Z= 4] and 5-hydroxymethylene-4-phenyl-(N-methyl)-1,2,5,6-tetrahydropyridine (II) [monoclinic crystals, space group P2(1)/n, Z= 4]-are determined by X-ray diffraction. In I, the weak intermolecular OH ... N hydrogen bonds link the molecules related by the a translation into homochiral chains. In II, the OH ... N hydrogen bonds link the molecules into infinite homochiral chains twisting about the crystallographic screw axes 2(1)(y). The helices are additionally strengthened by the short CH ... O contacts. (C) 2000 MAIK "Nauka/Interpeliodica".