The laser-induced fluorescence excitation of 3-hydroxyflavone, cooled by seeding in a supersonic expansion of He, was investigated in the range 28,000-28,500 cm-1. The vibronic origin of the S0-S1 (pp*) electronic transition of the unperturbed normal mol. form is at 28080.3 cm-1. The excitation spectrum is characterized by several progressions with vibrational spacing of 45 cm-1, and by severe spectral congestion at excess vibrational energy >225 cm-1. The prominent vibronic bands are best represented by Lorentzian lineshapes. The vibronic lifetimes, in the range 1.3-2.0 ps, are short because of excited-state intramol. proton transfer.