An actuating device for selecting shift positions of a shift-by-wire gearshift transmission. The actuating device comprises a selector lever that is movable between stable lever positions from at least one drive mode position to a parking lock position, a detent device with a spring-loaded detent element, a detent guide-plate and a separating device with an actuator-operated thrust wedge. The detent element and the detent guide-plate can be moved by the thrust wedge from a first position, in which the detent element engages in a shift track of the detent guide-plate, to another second position in which the detent element is disengaged from the shift track of the guide-plate. The actuating device enables automatic return of the selector lever to the parking lock position and thus provides the driver with correct visual and tactile feedback about the actual shift status of the transmission.