Mental disorders of cognitive and non-cognitive spectrum in the first-degree relatives of patients with Alzheimer's disease (AD) were studied in 134 relatives, mean age 47.6 years, including 110 children and 24 siblings of probands. Compared to the age-matched controls (22 normals without relatives with AD), the higher frequency of the following mental disorders was found in the relatives: Alzheimer's phobia, irritable weakness, mild cognitive impairment, including difficulties in learning new information and reduced sustained attention due to tiredness (2 times more frequent), difficulties in recollection of remote events (1.4 times more frequent), signs of constitutional cognitive deficit in the anamnesis (2-4 times more frequent), the combinations of two or three types of cognitive deficits (3-4 times more frequent), the combination of communicating hydrocephalus with MRI signs of cerebrovascular pathology (3,4 times more frequent). The data obtained in the study can help develop treatment/ rehabilitation measures to prevent the progression of cognitive deficit.