An exhaust gas aftertreatment system and a method of use reduces the amount of N2O produced in at least one of: (1) a selective catalytic reduction (SCR) catalytic converter and (2) an ammonia slip catalyst (ASC) in the exhaust gases from a combustion engine. The system includes an SCR catalytic converter arranged in an exhaust gas line upstream of an optional ASC. The exhaust gases pass through the SCR catalytic converter and any ASC before they are released by the exhaust gas outlet. An injector injects a reducing agent into the exhaust gases in the exhaust gas line upstream of the SCR catalytic converter at a dosing frequency F. A control unit generates a control signal to adjust the dosing frequency F so that the amount of N2O produced in at least one of: (1) the SCR catalytic converter and (2) the ASC is minimized while maintaining the amount of reducing agent added.