Introduction. Chemotherapy is currently the mainstay of treatment for patients with cancer, but despite its high efficacy, it has a number of drawbacks. With many interesting studies on chemotherapy-associated encephalopathy, absolutely no attention is paid to insomniac problems, which can also be “red buttons” for triggering cognitive and emotional disorders.Aim. To identify the features of neurological disorders in the form of dyssomnias and cognitive disorders in patients receiving chemotherapy.Materials and methods. The work was conducted in the chemotherapy department and was based on the results of the examination of 50 women undergoing chemotherapy courses with a diagnosis of malignant breast neoplasm. The study sample Introduction. Chemotherapy is currently the mainstay of treatment for patients with cancer, but despite its high efficacy, it has a number of drawbacks. With many interesting studies on chemotherapy-associated encephalopathy, absolutely no attention is paid to insomniac problems, which can also be “red buttons” for triggering cognitive and emotional disorders.Aim. To identify the features of neurological disorders in the form of dyssomnias and cognitive disorders in patients receiving chemotherapy.Materials and methods. The work was conducted in the chemotherapy department and was based on the results of the examination of 50 women undergoing chemotherapy courses with a diagnosis of malignant breast neoplasm. The study sample included women whose history excluded conditions that independently caused various disorders of the sleep process and cognitive impairment. The women ranged in age from 37 to 58 years, had no history of drug or alcohol dependence and no history of traumatic brain injury. All the patients were divided into 3 groups according to the number of chemotherapy courses (group I – up to 10 courses, group II – from 10 to 19 courses, group III – from 20 courses and more).Results and discussion. A tendency to worsening of insomniac disorders according to ISI was revealed in patients of the second and third groups in comparison with the first group (p > 0.05). The analysis of cognitive disorders severity values according to the MMSE scale similarly did not reveal reliable differences between the groups (p > 0.05), and there was a tendency for MMSE values to decrease with the increase in the number of chemotherapy courses. When calculating the correlation between the results of ISI and MMSE, we obtained an inverse high strength relationship (ρ = -0.8715). In other words, the more pronounced was the patient’s problem with the sleep process, the less she scored on the MMSE scale (more pronounced cognitive impairment).Conclusions. The results of this study will add to the data available in the scientific literature on the effect of cytostatic drugs on the CNS and provocation of encephalopathy with insomniac and cognitive disorders. The data obtained will be useful for oncologists, neurologists, rehabilitologists and specialists working with oncology patients.