A theoretical analysis of the chromophore xanthone has been carried out in various cases, starting from the isolated molecule and going on to the extremely polar-protic solvated chromophore. In the gas phase, we find that an El-Sayed forbidden channel with a rate constant of k(ISC) = 2 x 10(11) s(-1) is one of the trend-setting factors in the photophysical kinetics. The fluorescence is found to be quenched in the gas phase and polar-aprotic solvents. The analysis of xanthone in aqueous solution supports the delayed fluorescence model, which has been suggested to explain the high fluorescence quantum yield observed in water. Besides, we present a detailed analysis of the photophysics of xanthone in acetonitrile and methanol.