In a method for operating an exhaust gas after-treatment system for an internal combustion engine, the exhaust gas after-treatment system comprises at least one apparatus for generating a plasma and at least one SCR catalyst. The exhaust gas after-treatment system further comprises a device for metering a reactant for the SCR catalyst. According to the invention, the nitrogen oxides resulting from the operation of the apparatus for generating a plasma are taken into account in the method when metering the reactant for the SCR catalyst.