Abstract: The report is about giant false aneurysm of an extracranial part of the left internal carotid artery (ICA) in a patient aged one year and nine months. The reason of the complexity of diagnostics in this case was that the dissection of the ICA with formation of false aneurysm imitated the peritonsillar abscess' clinic. We have not found any descriptions of a similar cases of patients at such an early age in modern literature. References 1. Nikitina T.G., Kochurkova E.G., Petrosyan K.V., Alekyan B.G. Application of a stent-graft to correct a false aneurysm of the internal carotid artery. Creative. cardiol. 2015; 1: 66 [In Russ]. 2. Kalashnikova L.A. Dissection of arteries, blood supplying the brain, and disorders of cerebral circulation. Ann. clin. and exper. neurology. 2007; 1 (1): 41-49 [In Russ]. 3. Schievink W.I. Spontaneous dissection of the carotid and vertebral arteries. N. Engl. J. Med. 2001; 344: 898— 906. doi.org/10.1056/NEJM200103223441206. 4. 5. Kalashnikova L.A., Dobrynina L.A., Chechetkin A.O., Dreval M.V., Krotenkova M.V., Zakharkina M.V. Disorders of cerebral circulation in the dissection of the internal carotid and vertebral arteries. Algorithm of diagnostics. Nerve. disease. 2016; 2: 10-15 [In Russ]. 6. Kieslich M., Fiedler A., Heller C. et al. Minor head injury as cause and co-factor in the aetiology of stroke in childhood: a report of eight cases. J. Neurol. Neurosurg. Psychiatry 2002; 73: 13-6. 7. Seerig M.M., Chueiri L., Jacques J. et alt. Bilateral Peritonsillar Abscess in an Infant: An Unusual Presentation of Sore Throat. Case Rep Otolaryngol. 2017; 2017: 467015. doi.org/10.1155/2017/4670152. 8. Mazur E, Czerwinska E, Korona-Gtowniak I, Grochowalska A, Koziot-Montewka M. Epidemiology, clinical history and microbiology of peritonsillar abscess. Eur J Clin Microbiol Infect Dis. 2015 Mar; 34(3):549-54. doi.org/10.1007/s10096-014-2260-2.