The aim of this study was to determine the effects of diabetes mellitus, ovarian aging, ovarian aging plus diabetes mellitus, and the oxidative stress generated by these conditions on the lungs of rats, using histopatological and biochemical parameters. In the diabetic group, some abnormalities like bronchial hyperplasia, edema, haemorrhage, pulmonary capillary dilatation, breakdown of alveoli, mononuclear inflammatory cells, and moderate immunoreactivity were observed. Although, the results obtained from the ovariectomy group were similar to those of the diabetic group, haemorrhagic area and an increase in apoptotic cell density were observed more in this group compared to the diabetic group. In the last group, both immunoreactivity rate and the degree of abnormal structure were more remarkable compared to the other groups. Our biochemical results confirmed the histological findings. Conclusively, increase in the reactive oxygen species (ROS) levels of the cell, regardless of whatever reason, may lead to many other functional failures as well produce some disease conditions. Our results suggested that oxidative load increased in rats with ovariectomy-induced menopause with or without diabetes; however, enzymatic free radical defense mechanisms were damaged in the diabetic rats. The results also suggested that the antioxidant ability of the female sex hormone acts as a protective factor against diabetes.