Zinc oxide nanoparticles (ZnONPs) have been widely used in consumer and industrial products, especially in cosmetics, food additives, photo-electricity and rubber industry. The aim of the work was to evaluate toxic effect of 30 days administration of ZnONPs on lung and the ameliorative role of ascorbic acid in adult male albino rats. They received orally 400mg/kg/day of ZnONPs for 30 days and compared with others received the same dose of ZnONPs + 20mg/kg of ascorbic acid regarding GSH, NO, DNA damage and histopathological changes of the lung. Oral administration of 1/20 LD50 of ZnONPs for 30 days led to decrease in serum GSH, increased levels of NO, DNA damage detected by comet assay and histopathological changes in the lung in the form of collapsed alveoli, destruction of interalveolar septa with alveolar dilatation, thick interalveolar septa, heavy infiltration of inflammatory cells and inflammatory exudate. Ascorbic acid administration along with ZnONPs led to attenuation of oxidative stress and pulmonary toxicity induced by ZnONPs, but there was nonsignificant improvement in DNA damage proved by Comet assay. We concluded that ascorbic acid administration along with ZnONPs led to attenuation of oxidative stress and pulmonary toxicity induced by ZnONPs, but there was nonsignificant improvement in DNA damage proved by Comet assay.