Phenolic compounds are known to be present in high concentration in various of agro industrial wastes such as olive mill wastewater. As they are highly biorecalcitrant a possible treatment by Advanced Oxidation Processes has to be investigated. The photocatalytic degradation of the phenolic acids p-Hydroxybenzoic acid, Dihydroxybenzoic acid, gallic acid, vanillic acid, syringic acid) in the presence of TiO2 deposit on a glass plate has been reported. A comparison for the adsorption properties and the kinetics of reaction have been studied. The kinetics were found to be first order for all compounds and were compared with the compounds’ structures. The reaction rate for the compounds was found as the order Di-HBA < GA < p-HBA ≈ SA ≈ VA. The influence on the photdegradation rate of various parameters as pH, and substrate’s concentration was studied for p-Hydroxybenzoic acid only. It was found that the reaction is pH and substrate’s concentration dependence. A removal efficiency (50-70%) was determined after 5hr using UVlamp (15W- λ=360nm) and it increased up to 95% when H2O2 was added.