Theoretical study of several para-substituted O-nitrosyl carboxylate compounds has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries obtained from DFT calculation were used to perform natural bond orbital analysis. It is noted that weakness in the O3–N2 sigma bond is due to $$ n_{{{\text{O}}_{1} }} \to \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} $$ delocalization and is responsible for the longer O3–N2 bond lengths in para-substituted O-nitrosyl carboxylate compounds. It is also noted that decreased occupancy of the localized $$ \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} $$ orbital in the idealized Lewis structure, or increased occupancy of $$ \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} $$ of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are related with the resulting p character of the corresponding sulfur natural hybrid orbital of $$ \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} $$ bond orbital. In addition, the charge transfer energy decreases with the increase of the Hammett constants of substituent groups and the partial charges distribution on the skeletal atoms may approve anticipating that the electrostatic repulsion or attraction between atoms can give a significant contribution to the intra- and intermolecular interaction.