Laser flash photolysis studies (λ_exc = 355 nm, 10 ns pulse, 16 mJ/pulse) were performed to investigate the reactivity of the triplet excited state of 2,3-dimethoxy-9H-xanthen-9-one (1) towards several quenchers, in acetonitrile. The triplet 1 (λ_max = 380, 550 and 630 nm; τ = 3.0 µs, in acetonitrile) was efficiently quenched by 1,3-cyclohexadiene [k_q = (5.84 ± 0.18) x 10⁹ Lmol^-1s^-1], 1,4-cyclohexadiene [k_q = (7.15 ± 0.21) x 10⁵ Lmol^-1s^-1], and 1,4-diazabicyclo[2.2.2]octane (DABCO) [k_q = (7.15 ± 0.21) x 10⁵ Lmol^-1s^-1]. In the case of DABCO, the anion radical derived from 1 was clearly observed (λ_max = 410 and broad absorption in the 600-710 nm region). In the presence of phenol and its derivatives containing polar substituents (4-OMe- and 4-CN), a value of ~ 10⁹ Lmol^-1s^-1 was measured in all cases for the quenching rate constant. Photolysis (λ = 266 nm, 10 ns pulse, ~ 10 mJ/pulse) of 1 in 1:1 H₂O/acetonitrile solution leads to its photoionization, with the radical cation 2 formed showing absorption maximum at around 390 nm maximum and a wide band in the 500 to 650 nm region of the spectrum and a lifetime of 18.7 µs. The chemical characterization of this radical cation was performed employing nucleophilic species such as chloride, bromide, and acetate ions.