In photolysis of 4,4′-diazidodiphenyl sulfide quintet ESR peaks were observed and the plots of these signal intensities vs. temperature obeyed the Curie law, although no quintet signals were observed in the photolysis of 4,4′-diazidodiphenyl ether. The ESR spectrum upon the irradiation of 3,4′-diazidodiphenyl sulfide showed quintet resonances of 3,4′-dinitrenodiphenyl sulfide. Both Curie analysis and PM3-CI calculations indicated that the quintet state is a ground-state.