The mineralization and degradation of organic compounds present in waste water by heterogeneous photocatalysis has gained wide attention due to its effectiveness and tenancy to utilize UV-Visible solar light spectrum. The chemical stability, non-toxic character, magnificent electrical and optical properties have been recognized the ZnO as useful material for waste water treatment in environmental remediation technology. However, photocatalytic activity of ZnO limited to ultraviolet region because of its wide band gap (3.37eV). ZnO wide band gap obstruct photo-excitation for actual photocatalytic applications under abundant, safe and clean solar energy source. Many methods have been evolved in last decades to overcome this barrier. ZnO surfaces have been tailored with rare-earth metals to enhance its optical, surface and photocatalytic properties by different research groups. The doping with rare-earth metal ions enhanced the efficiency of ZnO photocatalyst by reducing band gap and shifted the absorbed wavelength to the visible region. This review paper compiles the attempts on modification of ZnO and their effect on photocatalytic activities by using rare earth metals.