Calibration of Positions of EEG Electrodes on a Subject

There is provided mechanisms for determining calibration of positions of EEG electrodes on a subject. A method is performed by a controller. The method comprises obtaining a set of signals representative of estimated positions for the EEG electrodes when placed on the subject. Each of the estimated positions represents a position of one of the EEG electrodes relative to the subject. The method comprises comparing the set of signals representative of estimated positions to a set of reference signals representative of reference positions. The set of reference positions represents intended positions for the EEG electrodes when placed on the subject. The method comprises determining the calibration of positions of the EEG electrodes using a difference between a property of the obtained signals and the set of reference signals.