The invention proposes an exhaust-gas purification unit for purifying the exhaust gas from an internal combustion engine which is preferably operated in lean-burn mode, in particular a diesel engine used in motor vehicles, in which a particulate filter and a SCR catalytic converter are arranged in the exhaust pipe in succession in the direction of flow, and having a reducing-agent supply, it being possible for ammonia to be added to the exhaust gas from the internal combustion engine on the entry side of the SCR catalytic converter by the reducing-agent supply. According to the invention, the exhaust-gas purification unit includes a hydrogen-generating unit for enriching the exhaust gas from the internal combustion engine with the hydrogen which it generates. Use in motor vehicles.