Biaxially stretched poly(ethylene terephthalate) (PET) foils and spin-coated PET films were analysed by surface-sensitive X-ray absorption spectroscopy (NEXAFS). The surfaces of partially crystalline foils and amorphous films can be easily distinguished when the angle of incidence of the linearly polarized synchrotron light beam is varied relative to the surface normal of the respective sample. In contrast to the amorphous state, we found a strong angle dependence in the NEXAFS spectra of the surface of crystalline samples.