Aging is accompanied by the rise of mental health problems and dementia. Their number by 2050 could reach 120 million people. The absens of classification of mental disorders of late age prevents from their correct diagnosis, forensic psychiatric assessment, promotes ageism. Kraepelin (1900) placed them in the category 'Interior body disease processes', and subdivided into 'arteriosclerotic', 'presenile psychosis of the age reverse development' and 'senile mental disorders'. Bleuler (1920) attributed them to 'Acquired psychosis with gross brain disorders. Organic syndrome'. Sternberg (1977) distinguished functional, vascular and atrophic forms. Shakhmatov (1996) believed that the classification of mental disorders of late age should basically be determined by the presence or absence of dementia. In ICD-9, ICD-10, DSM-5 there is no special section on mental disorders of aging. As a result there is a loss of such unique and specific syndromes of involution, as pseudoparalytic, frontal, paraphrenic disoders, acute and chronic Wernicke presbyophrenia, 'functional', delirium (involutional paranoid) and hallucinatory (Akboma dermatozoic delusion) psychosis of later age. ICD-10 consides a state of R54 'Old Age', but without pairing with category 'Mental disorders'. In the DSM-Y there is no section on mental disorders of old age, the only innovation is ontogenetic approach in the description of mental disorders, depending on different age periods and renaming of dementia into neurocognitive disorders, aimed at destigmatization of patients. The pilot version of the section 'Mental disorder' in the ICD-11 presents the category of 'Old age'. We believe that it is reasonable to classify 'Behavioral and mental disorders of late age' in this variant.