An arrangement and a method for influencing and/or detecting magnetic particles in a region of action is disclosed, which arrangement comprises:--selection means for generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength and a second sub-zone having a higher magnetic field strength are formed in the region of action,--drive means for changing the position in space of the two sub-zones in the region of action by means of a magnetic drive field so that the magnetization of the magnetic particles changes locally, wherein the selection means comprises at least one permanent magnet wherein the permanent magnet is at least partially shielded by an electrically high conductive shielding means.