A set of electronic properties calculated at the B3LYP/LACVP(d) level of theory for four cobalt macrocycles containing a ligand like porphyrin (CoP) and a benzoporphyrin (CoTBP) has been analyzed. The effect of aza nitrogen atoms (aza-N) present in the ligand (CoTAP, CoPc) on the electronic properties chosen has been studied. For the pair CoP/CoTAP we found a notorious effect of the presence of aza-N atoms in each electronic property studied. However, for the pair CoTBP/CoPc a different result was obtained. The dipole moment and the atomic charges, the latter evaluated on the cobalt atom and on the aza-N atoms, do not show the isolated effect of the aza nitrogen atoms and rather it appears to be mixed with the effect produced by the ligand size. On the contrary, electronic properties such as spin density and electrostatic potential evaluated on the cobalt atom clearly show the effect of the aza nitrogen atoms predicting that the latter present an electron withdrawing behavior in this kind of molecules