A method for reducing the particle and nitrogen oxide proportion in an exhaust gas flow of an internal combustion engine includes supplying a reducing agent to the exhaust gas flow, subjecting the exhaust gas flow containing the reducing agent to particle filtering, and then carrying out a selective catalytic reduction of at least a portion of the nitrogen oxides in the exhaust gas flow. The method and an exhaust gas treatment unit make it possible to simultaneously reduce the proportion of particles and nitrogen oxides in the exhaust gas. Ammonia, in particular, is used as the reducing agent. Regeneration of the particle filter is promoted by leading an ammonia-containing flow of gas through the particle filter. The method and device make it possible to consume less fuel with the same reaction rate and, at the same time to reduce available installation space, in comparison with existing corresponding prior art systems.