Objective: The pathological mechanisms of gestational trophoblastic disease have not yet been clearly determined. It is thought that oxidative damage contributes to the process. The aim of this study was to determine the levels of coenzyme Q10 (CoQ10), DNA damage, and lipid peroxidation in patients with hydatidiform mole. Materials and Methods: The authors studied the levels of CoQ10, 8-hydroxydeoxyguanosine (8-OHdG), malondialdehyde (MDA) by high-performance liquid chromatography (HPLC), and the activity of glutathione peroxidase (GPX) by spectrophotometric method in blood obtained from patients with a complete hydatidiform mole (n=29), healthy pregnant women (n=29), and healthy non-pregnant women (n=29). Results: The 8-OHdG/dG ratio (2.8148 +/- 0.81592) and MDA (10.8341 +/- 4.64875 mu mol) were significantly higher in patients with complete hydatidiform mole, while the ubiquinol-10/ubiquinone-10 ratio (0.2107 +/- 0.15675) and GPX activity (43.4606 +/- 18.31694 mU/ml) were lower (p < 0.001). Conclusion: The authors suggest that both mitochondrial oxidative and oxidative DNA damage play important roles in the pathogenesis of complete hydatidiform mole. Therefore supplementation of CoQ10 prevents recurrent gestational trophoblastic disease.