Objective. To compare thе medical history, clinical features, composition of cerebrospinal fluid (CSF), results of laboratory and instrumental examinations of patients with acute neuroinfections and differentiable diseases including a pseudoinflammatory variant of the acute stage of uncomplicated subarachnoid hemorrhage (SAH), consequences of traumatic brain injury (traumatic SAH, SAN combination with secondary purulent meningitis, posttraumatic nasal liquorrhea, intracerebral hematomas), abscesses and tumors of the brain, lymphoma with proven CNS. These diagnoses were mistakenly made to patients admitted to an infectious department. Material and methods. Forty-six patients, aged from 18 to 83 years, hospitalized in the Department of neuroinfections and intensive care in 2010—2016 were examined. Conventional clinical neurological, laboratory, instrumental (including MRI) examinations of patients, comprehensive examination of CSF samples, the study of markers of inflammation (C — reactive protein, CSF lactate), immunophenotyping of CSF cells were performed. Results and conclusion. The misdiagnosis can be explained by the overestimation of such symptoms as the acute (in most cases) onset of the disease with increased body temperature to febrile levels, presence of meningeal syndrome, disorders of consciousness and focal symptoms of varying severity. The authors showed the errors and difficulties in the diagnosis, the role and importance of an integrated, interdisciplinary approach taking into account history, clinical data, results of CSF study, conventional and special methods of laboratory and instrumental examination of patients.