A scroll pump includes a pump housing, a drive shaft having a concentric shaft portion and an eccentric shaft portion connected to an orbiting scroll. The shaft is driven by a motor so that rotation of the shaft imparts an orbiting motion to the orbiting scroll relative to a fixed scroll for pumping fluid between a pump inlet and a pump outlet of the compressor. The fixed scroll has an opening through which the shaft extends and is connected to the orbiting scroll on an opposing side of the fixed scroll to the motor. An anti-rotation device is located in the high vacuum region for resisting rotation of the orbiting scroll and allowing said orbiting motion, and a bearing arrangement for supporting rotation of the concentric shaft portion and eccentric shaft portion is located in tile low vacuum region.