The results of oxidation of surface layers of irradiated films made of low-density polyethylene (LDPE), isotactic biaxially oriented polypropylene (BOPP) and poly(ethylene terephthalate) (PET) are discussed. The films were modified in the air atmosphere using a high-energy electron beam generated by a linear accelerator. Oxidation of surface layers of 3.7 nm thickness upon doses of up to 500 kGy was investigated by X-ray photoelectron spectroscopy. It was found that the extents of oxidation were ca. 22, 11 and 8% for BOPP, LDPE and PET, respectively.