The meso substituted NI(II)(5,15-diNO(2)-octaethylporphyrin) coexists in at least three different conformers in CS2. To explore the structural properties of these conformers, we measured the resonance excitation profiles and depolarization ratio dispersions of various prominent Raman lines of Ni(5,15 diNO(2)-octaethylporphyrin) in CS2. The data were analyzed by a theoretical approach, which formulates the Raman tenser in terms of vibronic coupling parameters that depend on static deformations along the normal coordinates. The coupling parameters were determined by simultaneously fitting the depolarization ratio dispersion data and the corresponding resonance excitation profiles. We have also performed molecular mechanics calculations to identify all possible stable conformers of the molecule. To quantify the out-of-plane distortions of the calculated structures, we subjected them to normal coordinate deformation analysis (Jentzen, W.; Song, X.-Z.; Shelnutt, J. A. J. Phys. Chem. B 1997, 101, 1684). The results obtained from the Raman data and from molecular modeling are consistent in showing that the most stable conformers are strongly affected by rhombic in-plane (0.3 Angstrom) and ruffling (2;1 Angstrom) and doming (0.5-0.6 Angstrom) out-of-plane distortions. Additionally, smaller contributions from saddling were also obtained (similar to0.1 Angstrom). The three conformers detectable from the analysis of the Raman spectra most likely differ in terms of saddling and doming. The lowest-energy calculated conformers all show a horizontal orientation and out-of-plane position of the NO2 groups with respect to the macrocycle, but the conformers differ in the orientations of the ethyl substituents. Conformers with vertical orientations of the NO2 groups are calculated to be slightly higher in energy. INDO/s calculations reveal that the horizontal NO2 group orientation, and to a lesser extent the vertical orientation, gives rise to a strong admixture between porphyrin and NO2 molecular orbitals, enhancing the above distortions and leading to a break down of the 4-orbital model. A comparison with monosubstituted Ni(II)(5-NO2-OEP) reveals that all distortions increase with increasing number of nitro substituents. Altogether, this study demonstrates that meso nitro substitution of metalloporphyrins has a significant impact on electronic as well as structural properties of the ground and excited electronic states.