In the present study, it has been demonstrated that polymers containing pendant hydroxyl groups can undergo photoinduced crosslinking upon irradiation in the presence of bifunctional benzodioxinone. Irradiation of the copolymers of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) in dichloromethane ant THF solutions or in films containing bisbenzo-dioxinone, namely 5-[9-(4-oxo-2, 2-diphenyl-4H-benzo-[d][1,3]dioxin-5-yloxy) nonyloxy]-2,2-diphenyl-4H-benzo[d][1,3]dioxin-4-one resulted in the formation of insoluble networks. Model studies using monofunctional napthodioxinone, namely 7-hydroxy-2,.2-diphenyl-4H-naphtho[2,3-d][1.3]dioxin-4-one, revealed that crosslinking occurs via iinterchain ester formation between photochemically generated keten intermediates and pendant hydroxyl groups.