Abstract: In order to prevent minor deviations from expected operation in a yawing system before they lead to larger deviations, there is in accordance with a method aspect of the invention disclosed monitoring and determining deviation from an expected operation in a yawing system of a wind turbine. The method includes inputting a rotation angle input to at least one of a plurality of yaw motors, sensing an angular output of at least one of the plurality of yaw motors, receiving the rotation angle input to the at least one of the plurality of yaw motors in a signal processor, receiving the angular output of the at least one of the plurality of yaw motors, comparing at least two of the received signals, and/or comparing a mathematical relation of two of the received signals with a reference, and hereby determining whether there is any deviation from the expected operation.