Abstract: The results of quantum chemical calculations for isolated molecules of pentaammine-(5-cyano-2H-tetrazolato-N²)cobalt(III) perchlorate, pentaammine-(5-nitrotetrazolato-N²)cobalt(III) perchlorate, tetraammine-cis-bis(5-nitro-2H-tetrazolato-N²)cobalt(III) perchlorate, and tetraammine-cis-bis(1-methyl-5-aminotetrazolo-N³,N⁴)cobalt(III) perchlorate, as well as of the products of their possible initial decomposition stage were presented. The energetics and pathways of such reactions were determined. For the first time with the use of quantum chemical calculations it was shown that the decomposition of cobalt amminates can start with destruction of the tetrazole ligand and elimination of molecular nitrogen, rather than with dissociation of the coordinated ammonia molecule from the inner sphere of the cobalt(III) complex. The activation and dissociation energies of these processes were determined.