<br><b>Introduction:</b> Infectious mononucleosis is an acute, mild infection occurring mainly in childrenand adolescents. A characteristic feature is the presence of a symptomatic which includedfever, cervical or generalized lymphadenopathy, tonsillitis, coryzam and characteristic whitecoating on the surface. Laboratory tests show changes in the amount of leukocytes and theappearance of virocytes in peripheral blood as well as an increase in liver enzymes. The virusmainly infects epithelial cells and B lymphocytes. In B lymphocytes it intensively multiplies,leading to their transformation into plasma cells and, as a result, the production of specificIgM class antibodies. The produced antibodies activate T lymphocytes (CD8+). During theinfection, the humoral response is also activated. It works by producing antibodies directedagainst early antigen (EA), nuclear antigen (EBNA) and capsid antigen (VCA).</br><br><b>Aim:</b> The objective of the current study was to assess the occurrence of IgM and IgG antibodiesagainst the Epstein-Barr virus in children hospitalized in the Podlaskie Voivodeship.</br><br><b>Material and methods:</b> The levels of antibody were determined in serum patients serum usingthe ELFA method (Enyzme Liked Fluorescent Assay) using the VIDAS analyzer.</br><br><b>Results:</b> Based on preliminary studies, it shown that children aged 4-10 and 15-18 are the mostvulnerable group. The analysis of the conducted studies also showed that the acute phase ofinfectious mononucleosis is more often observed in female children.</br><br><b>Conclusions:</b> In order to better illustrate the seroepidemiological status of EBV infection,similar analysis should be performed in children all over Poland. In order to precisely identifythe target age group of children for possible vaccination, these studies should be extended.</br>