Abstract Investigations have been made on erythrosine sensitized photolysis of 4-diethylaminobenzene diazonium salt 1 and 2-diazo-1-oxo-1,2-dihydronaphthalene 2 in polymeric binders of different glass transition temperatures (T g 30–185°C). In the case of 1 the efficiency of photolysis as well as the quenching of direct and delayed fluorescence increase with decreasing T g ; in the case of 2, however, they increase with increasing T g . The addition of plasticizers causes analogous effects. It is assumed that the sensitization of 1 occurs preferentially from the S 1-state, whilst in case of 2 it is from the T 1-state of erythrosine. Probability calculations reveal that the effective concentrations of the reactants within the critical radius of electron transfer are low, accounting for the low efficiency of the sensitized photolysis.