Noben (idebenone) was administered in dosage 120 mg during 6 months to 35 patients, aged from 60 to 86 years, with dementia, Alzheimer's type and mixed type, and with memory disturbances which did not reach the level of dementia. The assessment of patient's state before and after treatment was based on the results of somatic, neurological and psychiatric examination as well as neuropsychological testing and using of psychometrical and other scales. The significant improvement on the MMSE scale was found in patients with mild and moderate dementia. The improvement of daily activity was observed in 27% of patients. The neuropsychological study revealed the improvement of short-term and delayed memory and attention, speech functions, the performance on kinesthetic, spatial and dynamic praxis tests, visual-spatial gnosis, reasoning and writing. The positive therapeutic effect assessed by the CGI scale was observed in 37% of patients, the stable state--in 48%.