Lichen ruber planus of the oral mucosa (LRP OM) is considered as a comorbid state. It is known that abnormal carbohydrate and lipid metabolism can worsen the course of the disease. Patients with LRP OM often have undetected carbohydrate metabolism disorders, which leads to a long-term recurrent course of dermatosis torpid to treatment. Objective — the study was aimed at evaluating the characteristics of the course of LRP OM in patients with impaired glucose metabolism (metabolic syndrome and type 2 diabetes mellitus). Material and methods. We carried out a complex clinical and laboratory examination of 34 patients aged 41 to 86 years (mean age 61.9±11.4 years) diagnosed with LRP OM. All patients underwent clinical and biochemical blood analysis, including assessment of glucose, insulin, glycated hemoglobin, and blood C-peptide levels and calculation of insulin resistance index. Stomatological status and characteristics of the course of LRP OM were determined. Results. Examined patients with metabolic syndrome were mostly diagnosed with typical (50% of cases) and atypical form of LRP OM (25%). Erosive-ulcerative LRP OM dominated in group 2 patients (66.7%). High intensity of caries and unsatisfactory hygiene of the oral cavity were detected in both groups of LRP OM patients. Inflammation of the gingival papillae is characteristic of patients with metabolic syndrome, and inflammation of the papillary and marginal gingiva is characteristic of patients with type 2 diabetes mellitus. Conclusion. The identified features of the course of LRP OM should be taken into account for diagnosis and prognosis of the disease.