DNA methylation is reversible, heritable epigenetic change that occurs at some stage in our lives. It is believed that DNA methylation changes with age and in carcinomas. Altered DNA methylation is one of the possible factors responsible for different human diseases. The model on which we explore changes in DNA methylation in the disease are potentially malignant lesions of the oral mucosa, oral lichen planus (OLP) and oral lichenoid lesions (OLL), that are difficult to distinguish clinically and histopathologically. Some epigenetic biomarkers could point to changes even before they can be clinically detected. Thus, we examine certain gene methylation status in healthy subjects and in those with changes in the mucous membranes of the oral cavity. The idea is to examine the methylation status of tumor suppressor gene RARB2 and genes involved in cell cycle regulation, transcription, apoptosis, differentiation and chromosomes repair (CCNA1, C13ORF18, hTERT1, hTERT2, TWIST1). In our previous studies we found that different methylation of these genes could be a good biomarker of mucosal diseases of the cervix. So, the assumption is that these genes could be changed substantially in the mucous membranes of the oral cavity, particularly in the diagnosis of OLP and OLL. Our study group include healthy subjects and patients of different ages with diagnosis of OLP and OLL. The expected result of the research is to get a change of methylation profiles according to age, in addition to the difference in healthy and ill condition. Therefore, the end result would be a resolution of at least one or some of the genes as good biomarkers for diseases of the oral cavity, which could be implemented in clinical practice.