The X-ray crystal structures of an inclusion compound with 3-picoline and two free host structures, all based on lactic acid but having different aryl substitution and optical resolution states (S or RS), are reported. They are the 2:1 complex of (S)-1,1-bis(p-tert-butylphenyl)-1,2-propanediol with 3-picoline, (5) [(S)-1,1-bis(p-tert-butylphenyl)-1,2-propanediol-3-methylpyridine (2/1), 2C(23)H(32)O(2).C6H7N], (S)-1,1-bis(p-methylphenyl)-1,2-propanediol, (6), C17H20O2, and (RS)-1,1-bis(1-naphthyl)-1,2-propanediol, (7), C23H20O2. The main structural differences between the host molecules in the three compounds are in the conformation of the phenyl or naphthyl rings. The influence of these rings is reflected in the elongation of the C(1)-C(2) bond in the propanediol moiety [up to 1.560 (5) Angstrom] and in the angular distortion of the tetrahedral angles around C(2). The hydroxyl groups play an important role in the crystal packing in all three. Significant differences between these structures and those of the corresponding unsubstituted phenyl host and inclusion compounds are observed.