The non-uniformity of photo-oxidation across polyoctenamer films has been investigated by bulk and surface analysis. Standard transmission FTIR (TIR), photoacoustic (PAS), internal reflection spectroscopy (ATR) and hydroperoxide titration give a detailed picture of the spatial distribution of photo-products to characterise the depth profile of degradation. Our finding is that the chemical oxidation profile develops from the very beginning of irradiation of polyoctenamer at λ >300 nm. We assume that the distribution of by-products is uniform in the superficial layer in the range 3-15 μm. Nevertheless a strong depth profiling of by-products is detected in bulk layers (>20 μm) and no photo-products are revealed by FTIR spectroscopy in the core of oxidised samples (>50 μm).