The influence of irradiation with accelerated electrons (energy 8.5 MeV, dose 5 kGy) on the physical properties of medical devices made of polyethylene terephthalate (PET) by infrared (IR) spectroscopy was studied. The revealed post-radiation changes in the IR spectra can be used to justify the choice of the dose of irradiation of PET products with electrons during the radiation sterilization procedure.