An extracorporeal shock wave lithotripsy system comprises a camera system for capturing images of visual references, a patient table, an ultrasound transducer and a therapy source, in particular a shockwave source. The patient table, the ultrasound transducer and the therapy source may each comprise a visual reference which may be detected by the camera system. This allows a precise positioning of the focus of the therapy source with respect to e.g. a kidney stone.