The crystal structures of C23H20N2O3 (I) and C22H18N2O2 (II) have been determined by single-crystal X-ray diffraction. These two compounds crystallise in the monoclinic space groups, P2(1)/c and C2/c. The structures have been determined by direct methods and refined to R, 0.041 (I) and 0.070 (II). The benzimidazole ring systems in (I) and (II) are planar. The phenyl rings attached to N1 and C2 in (I) are planar and make dihedral angles of 88.5(1) and 103.8(1)degrees with the benzimidazole ring systems. Corresponding angles in (II) are 95.0(2) and 105.1(2)degrees. (C) 1998 Elsevier Science B.V.