Abstract: A method for cutting trees (18) in the vicinity of a power line (10) using a topping saw (17) suspended from a helicopter (15) in such a way that the helicopter is flown in the direction of the power line (10) so close to the electricity wires (12) that the topping saw suspended from the helicopter cuts the desired tops of the trees. The cutting line (14) of the topping saw (17) is determined in such a way that the helicopter is flown with the help of a video camera (21) attached to the suspension bar (16) for the topping saw at an angle of 45° and a monitor (22) placed in connection with the helicopter's cockpit so that the video camera is kept directed towards the electricity wire (12) of the power line (10). The distance (a, b) of the point where trees are to be cut from the electricity wire (12) is determined by adjusting the distance (h) of the video camera from the cutting blade (20) of the topping saw (17).