Today there is a growing tendency in the prevalence of diseases caused by herpes viruses. At the same time there is an increase in the incidence of infectious mononucleosis, and the Epstein-Barr virus is one of its causative agents. The level of Epstein-Barr virus infection among the adult population of Ukraine has reached almost 100%, and more than 50% among the children. Epstein-Barr virus is a respiratory infection, and can be transmitted through saliva. According to statistic data, 85% of children are carriers of this virus, but it manifests itself only when immunity weakens. In many children, infectious mononucleosis occurs as an acute respiratory viral infection or quinine, and often paediatricians do not diagnose it. Usually children under the age of 10-14 are susceptible to the disease. In a large number of children, the course of infectious mononucleosis is quite similar to an acute respiratory viral infection or quinsy, and often paediatricians do not diagnose it. Usually children under the age of 10-14 are susceptible to the disease. The disease is characterized by feverish condition, sore throat, exanthema, enlargement of the lymph nodes, liver and spleen. All children with infectious mononucleosis manifest signs of tonsillopharyngitis that develops due to the growing activity of the opportunistic bacterial microflora, which densely colonizes the oropharyngeal mucosa in the immunocompromized condition caused by a herpes viral infection. At present, infectious mononucleosis plays a significant role in the overall infectious morbidity in children and is one of the leading causes of children hospitalization. Analysis of the case histories in patients aged 1-3, 4-6, 7-10, 11-15 and over 15 years through 2014-2018 has shown that infectious mononucleosis was predominantly diagnosed in male patients (222 cases) versus 150 cases of in female patients. The highest incidence of infectious mononucleosis has been registered among the residents of Lviv (287 cases) compared with the inhabitants of the Lviv region (85 cases). Regarding the age aspect, it has been found that the overwhelming majority of patients who have been diagnosed with an infectious mononucleosis are children under the age of 3 years.