Abstract: The present invention provides a method and device for determining depressive disorders or other mental disorders related to similar brain imbalances when the combination of powers of specific frequency bands in quantitative EEG has a certain positive or negative value. The present invention performs a signal-processing task to resting EEG recording, calculates the power of two specific frequency bands, finds the combination of the powers and evaluates the result. The method can be used as quick and easy noninvasive tool for diagnosing depression related problems in different patients as separate algorithm, as a part of an EEG recording and analysis device and as a separate device.