We present an electron spin resonance imaging (ESRI) study of spatial effects in the thermal degradation at 353 K of poly(acrylonitrile-butadiene-styrene) (ABS) containing 1 or 2% (w/w) Tinuvin 770 as the hindered amine stabilizer (HAS). The spatial distribution of the HAS-derived nitroxide radicals was obtained by 1D ESRI. Nondestructive ("virtual") slicing of the 2D spectral-spatial images resulted in a series of ESR spectra, which indicated the presence of nitroxide radicals in two distinct sites; their relative intensity varied with sample depth. The two spectral components were assigned to nitroxide radicals located in domains rich in butadiene (B) and in styrene-acrylonitrile (SAN), respectively. 1D and 2D ESRI allowed the study of chemical processes within distinct morphological domains as a function of sample depth and treatment time. Attenuated total reflectance (ATR)-FTIR spectroscopy of the outer layer (500 mum thick) of the polymer was used to follow the increase of the carbonyl concentration and the decrease of the butadiene peak with time of treatment. The ESRI and FTIR experiments showed that a larger Tinuvin 770 content in the polymer leads to less efficient stabilization. Improvement of the software for image reconstruction in 1D experiments enabled the visualization of an outer layer of thickness approximate to500 mum that is less degradable than the rest of the sample and believed to be formed during sample preparation by injection molding.