The aim of this study is the comparative evaluation of the serum levels of retinol in patients affected by leukoplakia and oral lichen planus. The study has been conducted through a statistical investigation with the purpose to underline possible variations of such levels, provided that meaningful, between the two groups. The retinol, an important molecule belonged to the family of retinoids, has an important anti-oxidant action and for this characteristic it can neutralize metabolic products (including reactive oxygen species), interfere with activation of procarcinogenes, prevent binding of carcinogens to DNA, inhibit chromosome aberrations, restrain replication of the transformed cell, suppress actions of cancer promoters and it may even induce regression of precancerous oral lesions. Leukoplakia and Oral Lichen Planus are oral precancer lesions with a greater potential of neoplastic malignant transformation that often show a strong subepithelial accumulation of inflammatory cells. Serum levels of retinol were estimated by the High Performance Liquid Chromatography (HPLC) method. Statistical analysis has been conducted with the Mann-Whitney U-test and we used P.A.S.T., ver. 1.53; a freeware developed by P.D. Ryan, D.A.T. Harper and J.S. Whalley in 1995 and up-to-date to the last version in September 2006. No significant differences were noticed in retinol serum levels in leukoplakia and oral lichen planus cases examined in this study. This result suggests that low serum retinol levels are not risk factors for occurrence of leukoplakia and oral lichen planus.