Comparison of the calculated and experimental IR and Raman spectra of a series of iodobenzenes showed that the C-I stretching vibrations for these compounds correspond to a very highly polarized Raman band at 150–270 cm−1 (ρ=0.1). The position of this band depends on the mass of the para substituent and relative position of the fluorine and iodine atoms in the molecule. The UV absorption spectral data indicate an interaction of the iodine atom and para substituents through the π-system. Opposite substituent effects on the change in intensity of the B-band in the UV spectra of iodobenzenes and tetrafluoroiodobenzenes were noted.