Heterophasic propylene-ethylene copolymers (HPEC) containing 1 wt % bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770) as a hindered amine stabilizer (HAS) were aged by exposure of approximate to 3 mm thick plaques to UVA and UVB sources in weathering chambers at 318 K. Two types of copolymers, HPEC1 and HPEC2, were examined, which contained 25 and 10 wt % ethylene (E), respectively, as ethylene/propylene rubber (EPR). Spatial and temporal effects of the aging process were studied by electron spin resonance (ESR) and ESR imaging (ESRD of HAS-derived nitroxide radicals (HAS-NO), by comparison of thermal transitions in original and aged samples using DSC, and by measuring the UV-vis absorption of HPEC films as a function of their thickness. ESR spectra indicated the presence of nitroxide radicals in two amorphous sites, fast (F) and slow (S). The spatial distribution of HAS-NO was obtained by 1D ESRI. Nondestructive ("virtual") slicing of the 2D spectral-spatial ESR images resulted in a series of ESR spectra that reflected the variation of the F/S intensity ratio with sample depth. HAS-NO was detected on the nonirradiated side due to the small, but not negligible, intensity of UV light transmitted through the plaque; on this side the nitroxide concentration remains high because it is not consumed in stabilization processes, as the local rate of degradation is low. Both ESRI and DSC experiments indicated a higher degradation rate in HPEC2, which contained more polypropylene (PP), 90 wt %; in these samples the degradation was accompanied by an increase in the extreme separation in the ESR spectra, indicating slower dynamics as a result of the increased degree of crystallinity. The degradation was also more advanced in samples exposed to UVB radiation compared to UVA due to the higher UV absorption coefficient in the shorter A range. The different effect of EPR content in thermal and UV aging of HPEC samples was discussed.