Abstract The Raman bandwidths and the frequency shifts of the ν 12 (A 1 ) mode and the IR ν 3 (OH) stretching mode of phenol and phenol-OD have been measured as a function of concentration in benzonitrile and benzene solutions. Opposite isotope effects of deuterium substitution in the hydroxyl group of phenol on the bandwidths of the ν 12 and the ν 3 (OH) modes have been found. The experimental bandwidths are discussed in terms of available theoretical models for dephasing and other mechanisms of broadening. The isolated binary collision dephasing model of Fischer-Laubereau, the Knapp-Fischer concentration-fluctuation model and the Robertson-Yarwood model have been tested. It has been stated that the purely repulsive potential is responsible for vibrational dephasing of the ν 12 mode of phenol in benzene while the concentration-fluctuation model reproduces the experimental data for that mode in benzonitrile. The coupling between the ν 3 (OH) and ν 2 (OH…N) modes is the dominant mechanism for broadening of the ν 3 (OH) mode of phenol in benzonitrile.