Abstract: The disclosure involves a method for reducing the content of NOx and N2O in gases. The method includes the conduction of a gas containing N2O and NOX over a series of two catalyst beds containing of one or more zeolites charged with iron followed by the: addition of a reduction agent for NOX between the catalyst beds. The first catalyst bed reaction zone is used to degrade the N2O and the catalyst bed second reaction zone reduces the NOX and breaks down at least part of the remaining N2O. The inventive device comprises at least one radially traversed catalyst bed.