Phenanthrene is considered to be a hazardous pollutant and is listed as a priority pollutant by the U.S. EPA. This laboratory study was designed to investigate the degradation of phenanthrene in water solutions by ozone, by ozone in combination with hydrogen peroxide and UV-radiation and by UV-radiation only, to compare the efficiency of different oxidation processes at different values of pH = 3, 7 and 9. On the basis of kinetic curves of phenanthrene destruction, the chemical reaction rate constants were calculated. The results obtained confirmed that phenanthrene oxidation proceeds mostly with molecular ozone and the best method for reducing its concentrations is an ozonation in neutral medium. The rate of phenanthrene autoxidation is rather slow and does not depend on pH nor H2O2addition. UV-radiation alone is also unable to reduce phenanthrene concentration significantly.