The nature of the lowest excited state for coumarin and some derivatives was investigated using steady-state and time-resolved fluorescence data at room temperature, as well as fluorescence anisotropy at 77 K in nonpolar and polar solvents in conjunction with theoretical data obtained with different methods : INDO/S-Cl, CNDO/ S-CI, MNDO-CI, and AM1-CI. The results show that S-1 is actually n, pi* for coumarin in any solvent. Substitution with methoxy and methyl and/or chlorine and/or the increase of solvent polarity reduces the energy gap between the S-1 (n,pi*) and S-2 (pi,pi*) states, promoting the mixing of these states and finally inducing inversion to S-1 (pi,pi*) with trisubstitution and for the disubstituted case in dioxane:water (1:4). The presence of a lowest lying S-1 (n,pi*) mediates a large degree of radiationless processes in the singlet mannifold.