The invention relates to a device (40) for reducing pollutants, in particular nitrogen oxides, in an exhaust gas flow of an internal combustion engine, comprising a reducing agent (46), in particular a urea-water solution, which is stored in a storage tank (42), a metering module, in particular a nozzle (68), for injecting the reducing agent (46) into the exhaust gas flow, and a pump (56, 100) for delivering the reducing agent (46) from a suction point (62) in the storage tank (42) to the metering module via lines (58, 66). According to the invention, the pump (56, 100) lies beneath a reducing agent level (44) in the storage tank (42), and a non-return valve is provided. As a result of the non-return valve, the device (40) is prevented from refilling with the reducing agent (46) after the reducing agent (46) is completely sucked back from the device (40) after shutting off the internal combustion engine, in particular after extended idle times of the internal combustion engine. In a first embodiment, the non-return valve is a filter (64) that is formed with a plurality of screens (80, 82, 84, 86) which are connected one behind the other, which have a special microstructure, and which are formed with a plastic material. In the case of a second embodiment, the non-return valve is formed with a hermetically sealing valve (158) which is heavily preloaded by a spring force in particular and which is directly integrated into the pump (100) that is necessary for delivering the reducing agent (46) in the device (40).