The photo-oxidation of poly(α-methylstyrene) (PαMS) has been studied by FTIR and mass spectroscopy. The samples have been submitted to various conditions of irradiation under oxygen, with different irradiation sources and at several temperatures. SF4 and NH3 treatments and photolysis under vacuum have been carried out on the photo-oxidized samples. The results obtained were compared to those obtained in the same conditions of irradiation for polystyrene samples. An identification of the photoproducts is proposed with their main ways of formation.