Clusters of up to four methanol molecules attached to Coumarin 151 exhibit large electronic red shifts ranging up to 3414 cm(-1). Experiments involving infrared-optical double-resonance spectroscopy (3100-3800 cm(-1)) show that different cluster cm sizes involve different attachment sites on the coumarin molecule. The n = 1, 3 and 4 clusters are evidently attached to the NH2 group, the 3 and 4 species being cyclic, whereas the n = 2 species most likely attaches via proton donation to the > C=O group. The structure assignments are supported by the results of semiempirical calculations.