The positional isomers of chlorophenol and dichlorphenol were separated by high-performance liquid chromatography using f3-cyclodextrin as mobile phase additives. Effects of β-CD concentration and methanol content of mobile phase on the separation of solutes were examined. Chromatograms of three Chlorophenol isomers and six dichlorophenol isomers show that the effective separations were achieved on a commercial RPC18 stationary phase. The chromatographic results indicate that β-CD is an appropriate mobile phase additive for the separation of those solutes and the formation of inclusion complexes play a dominant role in the retention mechanism.