A series of Pd based nanocrystals were used to catalyze regioselective hydrogenation of p-phenylphenol (p-PP) to p-cyclohexylphenol (p-CP). The polar solvents such as THF, methanol and ethanol offered much higher selectivity to p-CP than nonpolar solvent. Concerning the effect of supports, the active carbon supported Pd nanocrystals show the best performance probably due to its hydrophobicity and high surface area. The best result with high selectivity (89.1 %) was obtained by using Pd/active carbon as catalyst when p-PP was 100 % converted.