The heterocyclic rings containing B, C and N atoms, also known as azaborines, are systematically studied. The electronic properties of these BCN rings are explored by using second order perturbation theory and their aromaticity is discussed by the nucleus independent chemical shifts. These heterocyclic rings are found to be chemically more reactive than benzene and borazine, due to smaller HOMO-LUMO gap and non-zero dipole moment. However, the aromaticity of these BCN rings is less than benzene but two or three times that of borazine. (C) 2015 Elsevier B.V. All rights reserved.