ABSTRACT The importance of vitamins in the prevention of cancer has attracted the attention of physicians, nutritionists and scientists for decades. The mechanisms of carcinogenesis, extended in the context of the function of some vitamins, i.e. regulation of and participation in metabolic processes in the cell, suggest a substantial impact of these compounds on the initial stages of oncogenic cellular transformation. DNA methylation is an epigenetic modification critical to normal genome regulation and development. The vitamin folate is a key source of the methyl group used to DNA methylation. In light of these pathways, folate became a subject of interest as compounds whose deficit can potentially have an impact on the processes of carcinogenesis. This review consists of date about folic acid and cancer risk for fertile women and highlights the role of DNA methylation in normal genome function, how it can be altered, and the evidence of the role of folate/folic acid in these processes. As well the authors provide a up-to-date review of the literature regarding the relation between COC use and carcinogenesis in different organs. The risk of developing ovarian cancer and endometrial cancer in women using COCs is at least 50%, including carriers of mutations BRCA 1/2, smaller than in other women. Also contains data on preventive effects of COCs for other tumors. Thus, combination of COCs with folates is a component of the concept for long-term primary prevention of malignant neoplasms.