This study was designed to examine cytoprotective effects of boric acid and CoQ10 on a model of bleomycininduced lung fibrosis. A total of 32 female Wistar albino rats (200-250 g, n=8) were randomly divided into four groups (control, bleomycin, bleomycin + boric acid, and bleomycin + boric acid + CoQ10). Rats in the control group were given equal volumes of saline intratracheally. Lung fibrosis was induced by intratracheal administration of bleomycin hydrochloride (7.5 mg/kg in 0.9% NaCl) to rats under anaesthesia. In the treatment groups, the rats were treated with boric acid (10 mg/kg per day; perorally) and CoQ10 (4 mg/kg per day; intraperitoneally) for 30 days. All animals were sacrificed at the end of the experiment. The lung, liver, kidney, and spleen tissues were excised, taken for histopathological evaluation, and stored for the measurement of SOD and GSH-Px activities with trace element and minerals. As a result, boric acid and boric acid + CoQ 10 had preventive roles on bleomycin-induced lung fibrosis in rats.