The invention relates to an elevator comprising a hoistway, a vertically movable elevator car, a vertically movable counterweight at least one first rope interconnecting the car and counterweight and passing around one or more rope wheels mounted in proximity of the upper end of the hoistway, the weight of the elevator car being arranged to exert an upwards directed pull on the counterweight via said first rope, and the weight of the counterweight being arranged to exert an upwards directed pull on the elevator car via said first rope. The elevator further comprises a motor-driven winding device connected at least with the car or the counterweight for exerting a vertically directed pull on said only one of the car and counterweight for thereby changing the balance between the car and counterweight.