The surface modification of poly(ethylene terephthalate) films with polyfluorinated alcohols was studied. X ray diffraction analysis, differential scanning calorimetry, and IR Fourier spectroscopy were used to determine that a modifier has a combined effect on the supramolecular structure of the polyester. The fea tures of distribution of the modifier over the film surface are shown. The stabilizing effect of adding the mod ifier is discussed.