Photoluminescence (PL) and their excitation spectra, cathodoluminescence (CL) and thermoluminescence (TL) of PbWO4 crystals annealed in oxygen, air and vacuum have been investigated. The results indicate that the green luminescence is not caused by (WO3 + F) centers but is probably related to (WO4 + O-i). Assignment of the excitation states is also discussed. Some structural defects related to the oxygen vacancy (V-0) are the main mechanism inducing the fluorescence excitation band peaking at 378 nm and forming shallow traps corresponding to a TL peak at 134 K. The deeper traps shown by thermoluminescence at ca. 250 K originate from local oxygen excess defects.