Diesel oxidation catalysts promote chemical oxidation of CO and HC as well as the SOF portion of diesel particulates. They also oxidize sulfur dioxide which is present in diesel exhaust from the combustion of sulfur containing fuels. The oxidation of SO2 leads to the generation of sulfate particulates and may significantly increase total particulate emissions despite the decrease of the SOF fraction. Modern diesel oxidation catalysts are designed to be selective, i.e., to obtain a compromise between sufficiently high HC and SOF activity and acceptably low SO2 activity.