The results of the study of the spectral characteristics and photo cathodoluminescence zinc tungstate crystals subjected to heat treatment in an oxygen atmosphere, or flows of high-energy irradiation of oxygen ions. It was observed that additional introduction of oxygen leads to decline in luminescence's effectiveness. It was discovered, that introduction of oxygen by thermal processing leads to changes in excitation spectrum. Decline of excitation effectiveness proportional to increase of excitation quanta energy from 4.5 to 6.5 eV was observed; in the meantime, in the unprocessed crystals it declined by only 25-30%. The effect can be explained by destruction of complex defects with luminescence centers during introduction of additional oxygen. It was demonstrated, that characteristic oxygen's depth of entry during thermal processing is 20 nm.