By means of Raman scattering experiment performed on single crystals of solid nitromethane in various polarization geometries at normal pressure and low temperatures, the Davydov splitting of the vibrational levels in the solid phase of hydrogenated CH3NO2 and perdeuterated CD3NO2 nitromethane is reported for the first time. A re-examination of the lattice vibrations in their various symmetry species is also given. These experimental data are discussed on the basis of calculations using harmonic models of stretching, bending, and torsional motions of an isolated molecule and using density functional theory and second-order Moller-Plesset perturbation theory. Then, following Sorescu [J. Phys. Chem. B 104, 8406 (2000).], the intermolecular interactions (Buckingham 6-exp form plus charge-charge Coulombic interactions) were added to the intramolecular potential. The frequencies of the qapproximate to0 phonons or vibrons of different symmetry species were calculated paying a special attention to the symmetric and antisymmetric NO2 stretching modes whose wave numbers and bandwidths show specific behavior in solid phase transition induced by pressure at ambient temperature. The calculated Davydov splittings are in reasonable agreement with the observed ones with the largest deviation found just for the NO2 stretching vibrations. Finally, it emerges from the calculations that there is no pure torsion in the lattice region and that the mixed character of phonons (libration+translation+torsion) prevents the use of simple formulas for determination of the isotopic shifts.