Theoretical simulation of the bandshape and fine structure of the ν s stretching band is presented for 2,4-dithiouracil-H and 2,4-dithiouracil-D taking into account an adiabatic coupling between high-frequency N-H(D) stretching and low-frequency intermolecular N...S stretching modes, and linear and quadratic distortions of the potential energies for the low-frequency vibrations in the excited state of the N-H(D) stretching vibrations.In order to determine the low-frequency vibrations, the experimental spectra of the polycrystalline 2,4-dithiouracil in the far infrared and the low-frequency Raman range have been recorded. The experimental frequencies in the low-frequency region are compared with the results of the HF/6-31 G * * and Becke3LYP/6-31 G * * calculations carried out for the 2,4-dithouracil dimer.