Epstein-Barr (EBV) and cytomegalovirus (CMV) fall into the group of herpesviruses. At some point of their life, the majority of the adult population comes into contact with both viruses, which can be found in the human body in a latent form. Primary and recurrent infections by these viruses in immunocompetent persons usually go clinically unnoticed. The risk group of people, in which viruses can lead to severe forms of the disease, are immunosuppressed and immunocompromised patients. The clinical picture of the risk group of patients varies from nonspecific to specific. Lesions in the oral cavity caused by EBV and CMV virus are usually opportunistic in nature and a reflection of compromised immunity of the patient, usually due to some other serious illness. Every dentist is required to diagnose oral lesions caused by this virus and implement timely treatment. They are also obliged to be familiar with the protocol of dental treatment in high-risk groups of patients and to implement that protocol in consultation with a doctor competent for treating a systemic disease that led to the development of an opportunistic infection caused by EBV and CMV virus.