Fourier transform infrared spectroscopy shows that benzoic acid and its derivatives can bind chemically to the surfaces of CdSe. The dipole moment of the adsorbed benzoate correlates linearly with changes in the semiconductor work function, as determined by vibrating capacitor (Kelvin probe) measurements. Because ligand adsorption does not induce significant changes in surface photovoltage, we conclude that changes in work function are due to changes in electron affinity rather than in band bending. This means that ligand adsorption does not induce charge transfer between the surface and the semiconductor but rather adds a surface dipole. Changes in band bending do occur, however, upon conventional etching.