Vacuum-ultraviolet (VUV) radiation causes the dissociation of organic a bonds such as the C-C and the C-H bonds in polyolefins. The radicals formed in this process were investigated by trapping with nitric oxide. PE, PP, and PS were irradiated in ultrahigh vacuum with the MgF2-filtered radiation of a hydrogen plasma. After an irradiation period of 1 h and an immediate radical trapping, PE, PP, and PS incorporate 1.4, 0.4, and 0.2 atom % nitrogen, respectively, measured by XPS. These nitrogen concentrations correspond to 5.4 x 10(20), 1.4 x 10(20), and 0.8 x 10(20) spins/cm(3), respectively. By the fitting of the XPS-N1s peaks, detailed information about the nitrogen functional groups and about the original radical types was obtained.