AbstractPhotochemical processes occurring in polystyrene films containing dicumyl peroxide (DCP), in the presence of octadecyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate (Irganox 1076) were investigated. It was found, that Irganox 1076 reduces the photo‐oxidation and photo‐degradation of polystyrene when DCP is used as an initiator of the processes and polymer samples are irradiated with light of λ