A device for treating exhaust gases includes a particle separator, an SCR catalytic converter for selectively reducing nitrogen oxides and an ammonia generator for generating ammonia as a selective reducing agent for reducing nitrogen oxides. The particle separator is provided in a main exhaust line and the ammonia generator is provided in a first secondary line. The first secondary line opens into the main exhaust line at a junction in such a way that an ammonia-containing gas stream generated in the ammonia generator can flow through the SCR catalytic converter. The method and the device advantageously permit the proportion of particles and nitrogen oxides (NOx) contained in the exhaust gas of an internal combustion engine to be reduced simultaneously, with the energy consumption for this reduction being small and at the same time the entire device being embodied as a compact unit.