Abstract By using the AM1 method on 4X and 4′X substituted 2′(OH)chalcones (X=H, OH, F, Cl, CH 3, CH 3O, N(CH 3) 2, and NO 2), certain currently unclear structural characteristics, conformational equilibria, intramolecular hydrogen bonds and UV spectroscopic properties had been clarified. The compounds studied have non-planar structures. The 2′(OH),4′Xchalcones only present the trans- s- cis conformation. trans- s- cis and trans- s- trans conformers of 2′(OH),4X-chalcones have a comparable thermodynamic stability. For these chalcones, a conformational equilibrium at 298 K exists, with 91% of the trans- s- cis form. The proposal of analyzing the intramolecular hydrogen bond of 2′(OH),4X-chalcones as an intramolecular proton-transfer reaction, is acceptable because the results and theoretical prediction of this study agree well with available UV spectroscopic experimental data.