The positioning appts. includes an substrate table (1), a subsystem for processing an object on the table, a drive unit (21) displacing the table, and a system (39) measuring the position of table w.r.t. the subsystem. The drive unit has a stationary part fastened to the positioning appts. machine frame co-operating with the measuring system's stationary and movable parts fastened to the table. The measuring system stationary part is fastened to the positioning appts. reference frame dynamically isolated from the machine frame.