The title compound, C(24)H(24)N(2)O(2), crystallizes as a triclinic polymorph from dimethylformamide and a monoclinic polymorph from ethanol. In both forms, the molecule displays crystallographic inversion symmetry, and the packing involves translationally related 'ladders' of molecules connected by N-H...O=C hydrogen bonds. Differences between the structures can be rationalized in terms of weak C-H...O contacts. Powder and differential scanning calorimetry investigations of new samples gave no evidence for the triclinic form, and it seems to represent a disappearing polymorph.