Abstract Infrared spectra of the products of one- and two -step reduction of both benzil and benzil-180 have been investigated in dimethylsulfoxide-d6 and tetrahydrofurane solutions. Anion-radicals have been obtained by electrochemical reduction of benzil and benzil-180; dinegative ions have been prepared by reduction of the same ketones with potassium mirror in vacuo. The band assignment has been performed using the group vibrational concept and isotopic shift data. The previous assignment of the C[dbnd]O stretching band of benzil anion-radical-has been discussed and corrected. Two bands in the infrared spectra of benzil dianion have been found to be sensitive upon 180 isotope labelling. This result certifies the presence of cis-configuration of benzil dianion in the investigated solutions. A decrease of ca. 290 cm-1 has been found for vC[dbnd]O after the transformation of the neutral benzil into an anion-radical. Conversion of benzil anion-radical into dianion has been accompanied by an additional vC[dbnd]O downward shift of 105 cm−1