The spectroscopic and photophysical properties of 1-methyllumichrome and four dimethyl-alloxazines absorbed on cellulose are presented. Time-resolved emission and transient diffuse reflectance measurements of the spectra and decay kinetics of dimethyl-alloxazines and 1-methyllumichrome on cellulose have provided information concerning the excited singlet and triplet states when these compounds are excited at 355 nm. The differences in the average fluorescence rate constant and in the value of the distribution parameter, γ, obtained for 1-methyllumichrome ( = 5.88 10 ⁸ s⁻¹ and γ = 0.03 ± 0.02) and for dimethyl-alloxazines ( = (1.75–3.57) 10⁸ s⁻¹ and γ = (0.6–1.0) ± 0.02) on cellulose are reported. The first diffuse reflectance laser flash photolysis spectra of these compounds have been recorded and at least two transient species with lifetimes of the order of microseconds and milliseconds have been observed.