The electronic structure, geometrical parameters and relative stability of the isomeric forms of N₂O₃ are analysed by means of ab initio calculations. Total energies of the different isomers are given. The energy difference between the most stable conformers of the symmetric N₂O₃ is 4.31 Kcal mol⁻¹ as provided by 6–31G basis set. The height of the rotational barrier determined by the ab initio technique is 7.12 kcal mol⁻¹.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exactas