Due to the high price of pure oxygen, to increase the competitiveness of the electrochemical wastewater treatment, it is interesting to evaluate GDE performance when fed with air. In a previous paper (Panizza and Cerisola, 2008) a preliminary study of hydrogen peroxide electrogeneration at a gas-diffusion cathode fed with air was carried out in low ionic strength solution under different conditions of pH, current density, and temperature and experimental results have indicated that gasdiffusion cathodes enable a considerable production and a good current efficiency, even when pure oxygen feed is replaced by air feed. Therefore, in the present paper we report the results about the treatment of model wastewater containing synthetic dye using hydrogen peroxide electrogenerated at a gas diffusion cathode fed with air.