CMV and EBV infections are common in humans. In immunocompetent persons those infections are usually asymptomatic but in immunocompromised can manifest as a severe disease. CMV is a common cause of congenital infections. It is also a frequent complication in transplant recipients. The aim of this study was to assess the prevalence of CMV and EBV infections among hospitalized children. Specific antibodies against CMV and EBV were detected in serum by ELISA test. Presence of CMV DNA was determined in leucocytes by Murex Hybrid Capture System. CMV and EBV infections were defined as the presence in serum IgM-class specific antibodies. Obtained results indicate that CMV and EBV infections are frequent in immunocompromised patients. Among patients with CMV or EBV infection, 40% have been diagnosed with cancer, most of whom with hematologic malignancies: leukemia or lymphoma. CMV and EBV coinfection was detected in 14% of infected children. Of all patients with CMV, 50% were neonates and infants. Congenital infection was diagnosed only in one case. The remaining infections were acquired during perinatal period or later.