Abstract— <p>A quantum-chemical study of the structure and conformational dynamics of mono- and difluoromethylcyclopropane molecules in the ground electronic state is presented. The conformational behavior of these molecules was studied, the relative energies of the conformers and the transition energies in the low-frequency region of the vibrational spectrum were calculated, and the minimum energy paths corresponding to the low-frequency vibrational modes were investigated. The energies of vibrational transitions were estimated both in the harmonic approximation and by solving anharmonic problems based on the variational principle in one- and two-dimensional approximations. Particular attention is paid to the analysis of the relationship between the torsional vibration (internal rotation) and other low-frequency vibrations.</p>