An exhaust gas after treatment system includes a diesel particulate filter unit arranged downstream of a diesel engine, a NO2 reduction catalyst arranged downstream of said diesel particulate filter, a selective catalytic reduction (SCR) arrangement arranged downstream of said NO2 reduction catalyst, a first injector for feeding reducing agent into the exhaust gas arranged downstream said particulate filter and upstream said NO2 reduction catalyst, a second injector for feeding reducing agent into the exhaust gas arranged downstream said NO2 reduction catalyst and upstream said selective catalytic reduction (SCR) arrangement. An exhaust gas after treatment method is also provided.