Fluorescence from the second excited singlet state (S-2) of 3-hydroxyflavone (3HF) has been observed for the first time in supercritical carbon dioxide (sc-CO2) environment. Steady-state experiments reveal that the intramolecular proton transfer is less effective from the S-2 state of 3HF compared to that from the S-1 state. (C) 2004 Elsevier B.V. All rights reserved.