Background:In everyday clinical practice, patients who seek dental care in case of oral mucosa diseases are one of the most difficult categories of patients due to difficulties in diagnosis and treatment. Materials and methods: The review and analysis of scientific and medical literature based on the Scopus, Web of Science, MedLine, PubMed, NCBI databases, the study of which does not exceed 5 years, including literature reviews and the results of clinical trials. Results: Changes in the oral mucosa can be clearly specific. Clinicians can make the correct diagnosis and determine the tactics of treatment by appearance. However, in most cases the diagnosis of diseases with this anatomical location is complicated, because the clinical picture is nonspecific and often burdened with additional local and general adverse factors. A detailed clinical examination and additional research methods are required to establish the correct diagnosis. Diagnosis of oral mucosa diseases is based on a careful assessment of clinical and laboratory data. Conclusions: Taking into account the prevalence of diseases of the oral mucosa, of particular interest is the question of the course of the process of differentiation of the epithelium of various anatomical zones in the norm and the mechanisms of restructuring of the cellular composition in pathological processes, with the cops of objectifying the diagnosis, predicting the course of the disease and pathogenetically substantiated treatment.