An apparatus for determining and/or monitoring at least one process variable of a medium and includes: A mechanically oscillatable unit, which executes mechanical oscillations in a direction and which is secured at a seating. Included is an exciting/receiving unit, which excites the mechanically oscillatable unit to mechanical oscillations and which receives the mechanical oscillations of the mechanically oscillatable unit; and a control/evaluation unit, which controls the mechanical oscillations of the mechanically oscillatable unit and which determines and/or monitors the process variable. At least one compensating mass is provided, which is mechanically coupled with the mechanically oscillatable unit and which is embodied and/or secured in such a manner that it executes mechanical oscillations in a direction, wherein the direction of the oscillations of the compensating mass are essentially perpendicular to the direction of the oscillations of the mechanically oscillatable unit.