Conformations of 2-chloro-N-[2-(methylsulfanyl)phenyl]-and 2-(diphenylthiophosphoryl)-N-[2-(methylsulfanyl)phenyl]acetamides have been studied by the dipole moment method and quantum chemical calculations. 2-(Diphenylthiophosphoryl)-N-[2-(methylsulfanyl)phenyl]acetamide has been found to exist as an equilibrium mixture of two conformers with synclinal and anticlinal orientations of the C sp 3-C sp 2 and P=S bonds. 2-Chloro-N-[2-(methylsulfanyl)phenyl]acetamide is represented by one preferred conformer.