Abstract: A process for removing impurities, in particular oxides of sulphur (SOx) and/or oxides of nitrogen (NOx) from oxygen-containing gas streams by scrubbing with at least one washing agent is described. In order to achieve effective gas purification in an economical manner even in the case of so-called large “oxyfuel” furnaces which operate with oxygen as fuel gas, it is proposed to convert the impurities at an elevated pressure of at least 2 bar with at least one basic constituent of the washing agent into salts and to wash out said impurities as dissolved salts.