An ion guide includes a plurality of curved electrodes and an ion deflecting device. The electrodes are arranged in parallel with each other and with a central curved axis, the curved central axis being co-extensive with an arc of a circular section having a radius of curvature, each electrode being radially spaced from the curved central axis, wherein the plurality of electrodes define a curved ion guide region arranged about the curved central axis and between opposing pairs of the electrodes. The ion deflecting device may include a device for applying a DC electric field to two or more of the electrodes in a radial direction. The ion deflecting device may include a pair of curved, parallel ion deflecting electrodes, which are in addition to curved electrodes utilized for applying an RF ion guiding field.