Abstract: The invention is a method of treating exhaust gases generated by a diesel engine by locating two catalyst components in the engine exhaust gas passage. The first catalyst component which exposed to oxidizing diesel exhaust is located nearest to the engine and is a nitrogen oxide absorbent made of support material carrying precious metal. The second component is a catalyst such as a lean-NOx catalyst or a selective reduction catalyst which is capable of converting the exhaust gas passing over it including reducing the nitrogen oxides desorbed from the first component into nitrogen (N2) or nitrous oxide (N2O). Materials like hydrocarbons or ammonia or urea may be injected into the vicinity of the second catalyst component to aid in the reduction.