Inclusion of 2,4-dihydroxyquinoline in a variety of cyclodextrins with different cavity dimensions is studied. It has been found that excited state proton transfer is strongly affected upon the inclusion of 2,4-dihydroxyquinoline in the nano cavities of cyclodextrin derivatives. Molecular encapsulation of 2,4-dihydroxyquinoline by -, , and methyl -cyclodextrins in aqueous media has been studied by steady state absorption and fluorescence emission techniques. It has been found that the fluorescence intensity at 360 nm increases in case of inclusion in -CD. On the other hand, the band at 360 nm decreases with concomitant increase of the fluorescence intensity at about 325 nm in case of the inclusion in -CD and M-CD. Calculation of the association constant shows that inclusion in -CD is higher than in case of M-CD and -CD