Cancer is an abnormal proliferation of cells in a tissue or organ that causes the cells to change their nature, eventually producing a lump or mass and spreading to other regions of the body in most cases. The purpose of this study is to evaluate the level of coenzyme Q 10 in breast cancer patients and to determine their relationship to the proliferation of breast cancer. This study has investigated 90 women (60 patients and 30 controls) subdivided according to stages of cancer status. This study shows the mean of coenzyme Q 10 was observed in breast cancer women (16.91±2.52) as compared with the healthy control group (42.49±7.45) the difference was highly significant at a P. value of 0.0003. The mean and stander deviation of coenzyme Q 10 in women with breast cancer (stage 1, stage2, stage3, and metastatic stage) were (28.03b±5.81, 17.51b±3.42, 22.71b±4.38, and 17.93b±2.92) in comparison with healthy women were(40.22a±3.13). It was concluded that the levels of coenzyme Q 10 were significantly decreased in breast cancer women as compared with healthy women.