The valence bands (VB) of remote oxygen and remote nitrogen plasma-treated polyethylene and polypropylene were studied to determine changes in the basic polymer structure. Each of the polymers showed a characteristic valence band profile, which retained much of its original shape after plasma treatment. This has suggested that even though plasma treatment can cause the incorporation of a high proportion of functional groups, significant segments of the original polymer structure remain unchanged within the x-ray photoelectron spectroscopy (XPS) sampling depth. Angle-resolved x-ray photoelectron spectroscopy (ARXPS) suggests that near the outer surface, the polyethylene structure is modified by branching and cross-linking.