Аннотация:The paper refers to the results of quantum–chemical calculations of structural parameters, enthalpy of formation, IR absorption spectra of some 5/6/5 tricyclic 1,2,3,4- and 1,2,4,5-tetrazines annelatedwith imidazoles. Methods of various complexity of the Gaussian program package, G4, G4MP2, M062X/6-311+G(2d,p), B3LYP/6-311+G(2d,p), ωB97XD/aug-cc-pVTZ, CBS-4M, have been used in calculations.