Adsorption of CF₄ on ZnO has been studied by means of FTIR spectroscopy at 55-300K. The contour of the band of the ν ₃ vibration in the spectra obtained is shown to depend crucially on surface coverage, due to strong resonance dipole-dipole interaction in the layer of adsorbed molecules. At high surface coverage the band is split into two components at 1320 and 1245cm^-1, about 75cm^-1 apart. The shape of the low frequency component is complicated by an "Evans hole" at 1258cm^-1. At lowest coverage only a weak band of ν ₃ vibration was seen at 1270-1272cm^-1; about 10cm^-1 below the corresponding wavenumber for gaseous CF₄. Preliminary adsorption of CO does not affect significantly the spectrum of adsorbed CF₄, leading only to slight decrease of the distance between the two components. Experimentally observed band contours were compared with those calculated theoretically using a model developed earlier for the spectra of interacting molecules in liquid phase, or dissolved in liquefied noble gases, and updated for the case of 2D systems. The calculated spectra reproduce well the splitting of the ν ₃ band for a monolayer, as well as the coverage and temperature dependence of the IR spectra.