Abstract: An exhaust system for a vehicle having a cab (53) and an internal combustion engine (1) located in an engine compartment (51). The system includes an exhaust gas treatment unit (9) located outside the engine compartment and having an inlet (9a) which receives exhaust gases from the engine and an outlet (9e) which passes treated gases into a final portion (E) of the exhaust system. The treatment unit (9) is arranged to extend generally vertically with the outlet (9e) generally vertically above the inlet (9a) and adjacent a corner post (52) of the cab of the vehicle to reduce impact on the visibility from the cab. A cage (C) surrounds the exhaust gas treatment unit (9) and has a support means (12) for attachment to a chassis of the vehicle and an outlet (15e) which the outlet (9e) of the treatment unit is connected.