The significant variety of psychopathological presentations of depression causes difficulties in its diagnosis. Depression of middle age is subdivided depending on the predomination of one or another disorder in the clinical picture. There are simple depression and complicated depression with additional psychopathological symptoms. The most difficult is to diagnose depression with onset in early childhood, including infant's age, when the psychopathological presentations depend on the consequences of the perinatal CNS lesion, maternal deprivation and other factors. In children, the clinical picture of depression differs by syndromologic incompleteness, peculiarity of phenomenological presentations and polymorphism of disorders. In adolescence, depression is characterized by the predominance of behavioral disorders, marked psychopathic-like disorders, suicidal attempts, higher frequency of bipolar forms. Depression with late age at onset differs by the abundance of somatic and hypochondriac complaints, anxiety and depressive delusion accompanied by the transitory aggravation of cognitive impairment (depressive pseudodementia).