Abstract: A method of simultaneously removing SO.sub.x and NO.sub.x from waste gases. Using a known desulfurization process the waste gases free of the acidic components are contacted with an oxidizing agent in the gas phase for the oxidation of the oxygen of nitrogen contained in the waste gases. The formed NO.sub.2 is absorbed in a subsequent absorbing stage under previous addition of NH.sub.3 and the thereby obtained absorbing product is oxidized to form ammonium nitrate in a subsequent oxidation stage with atmospheric oxygen and then reconveyed into the desulfurization process.