Authors have studied the psychopathological structure, risk factors and predictors of mental confusion in 102 patients with dementia of different etiologies (Alzheimer's disease (AD), cerebrovascular dementia (CVD) and mixed Alzheimer disease/vascular dementia). The high frequency (>40%) of mental confusion in patients with dementia admitted to geriatric departments of a psychiatric hospital has been identified. Mental confusion was most frequently characterized by a syndrome of memory and/or confabulatory confusion. The causes of mental confusion in elderly patients with dementia, including the exacerbation of a somatic pathology and changes in conditions of patient's staying in hospital, have been specified. The frequency of mental confusion is correlated with patient's age: more than 55% of cases has been noted in the group aged over 70 years. Mental confusion develops 6 times more frequent in patients with moderately severe and severe dementia than in those with mild dementia. Timely diagnosis and adequate treatment are predictors of favorable outcome in most patients. Treatment of this syndrome should be strictly differential. Antipsychotic treatment is needed in case of persistent psychotic symptoms and severe behavioral disturbances. Drugs for pathogenetic therapy of dementia have been used in the complex treatment of mental confusion in patients with dementia, in particular AD.