Cigarettes are transferred in batches adopting a procedure that includes the steps of feeding loose cigarettes en masse into a hopper with a back wall and two side walls delimiting a top inlet and a bottom outlet, also a shutter by which the bottom outlet is opened or closed, and actively varying the geometry of the side walls so that the internal volume of the hopper is adapted to accommodate the quantity of cigarettes admitted through the inlet, by means of an actuator mechanism connected to the side walls. Thus, it becomes possible to monitor and control both the rate at which the cigarettes flow into the hopper, and the pressure to which the single cigarettes are subjected while occupying the hopper and during the process of filling a tray.