Cervical intraepithelial neoplasia (CIN) may, at times, unpredictably progress to invasive carcinoma of the cervix. Epidemiological nutritional studies suggest that higher dietary consumption and circulating levels of certain micronutrients may be protective against cervical cancer. However, a preventive role of dietary antioxidants in CIN is not well established. The purpose of this cross-sectional study was to investigate the comparative plasma concentrations of three potent antioxidants, coenzyme Q10, α-tocopherol and γ-tocopherol, in women with normal Pap smears and patients with a biopsy-confirmed histopathological lesion diagnosed as CIN or cervical cancer. Plasma concentrations of coenzyme Q10, α-tocopherol and γ-tocopherol were measured by high-pressure liquid chromatography in both normal women without any history of abnormal Pap smears (n=48), and patients with histopathologically confirmed diagnoses of: (a) CIN I, n=98; (b) CIN II, n=49; (c) CIN III, n=10; and (d) cervical cancer, n=25. The mean plasma levels of coenzyme Q10, α-tocopherol and γ-tocopherol were significantly lower (P<0.001,<0.001, and<0.001, respectively by Kruskal-Wallis test) in patients with various grades of CIN and cervical cancer compared with controls. After controlling for age and smoking, an inverse association between histological grades of epithelial lesions and both plasma coenzyme Q10 and α-tocopherol concentrations was observed. The low plasma concentrations of coenzyme Q10 may be due to deficient dietary intake or a decrease in endogenous coenzyme Q10 biosynthesis that may reflect increased utilization as a result of free radical reactive oxygen species induced oxidative stress. Further molecular studies on the mechanistic role of antioxidants in women with precancer cervical lesions are needed.