The study deals with theoretical psychiatric proposals about relations between anxiety and depressive disorders. Three theoretical positions developed on the basis of numerous evidence on relationship of anxiety and depressive disorders: unitaristic (anxious and depressive disorders represent one disorder with different clinical pictures or phases of the disorder), pluralistic (there are two classes of disorders with clearly recognizable boundaries) and anxious-depressive position (mixed anxious-depressive disorder represents also a single disorder). Possible reasons for antagonisms, connections (i.e. lack of connections) to some proposals of psychologists are commented upon, as well as the significance of this problem for classification of mental disorders in general.