Despite the enormous biological significance, the structure-stability relationship in S-Nitrosothiols (RSNOs) that govern their activity in vivo is not well understood. We provide useful structural properties (bond length, vibrational frequency, dissociation energy, and interconversion barrier) of the -SNO group in RSNOs (R = H and CH3) using the recently suggested computationally cost-ffective multireference ab initio method which includes electron correlation effects by means of the perturbation theory using a multiconfigurational zero-order wave function. A sizable rotation barrier of cis-trans RSNO interconversion imply a partial S-N double-bond like nature. The low stretching frequency, elongated length, and small dissociation energy indicate that this bond is relatively weak and labile. Although the study of S– bond in RSNOs is a challenging case even for the current generation computational approaches, IVO-SSMRPT method (having several appealing features) employed here is competent to reproduce the structure and stability of RSNO isomers in close agreement with the reference high-level estimates. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.