Carbon monoxide (CO) attenuates lung ischemia reperfusion injury (IRI) via inhalation, and as an additive dissolved in flush/ preservation solution. This study observed the effects of lung inflation with CO on lung graft function in the setting of cold ischemia. Donor lungs were inflated with 40% oxygen þ 60% nitrogen (control group) or with 500 ppm CO þ 40% oxygen þ nitrogen (CO group) during the cold ischemia phase and were kept at 4 C for 180 min. Recipients were sacrificed by exsanguinations at 180 min after reperfusion. Rats in the sham group had no transplantation and were performed as the recipients. Compared with the sham group, the oxygenation determined by blood gas analysis and the pressure-volume curves of the lung grafts decreased significantly, while the wet weight/dry weight (W/D) ratio, inflammatory reaction, oxidative stress, and cell apoptosis increased markedly (P < 0.05). However, compared to the control group, CO treatment improved the oxygenation (381 AE 58 vs. 308 AE 78 mm Hg) and the pressure-volume curves (15.8 AE 2.4 vs. 11.6 AE 1.7 mL/kg) (P < 0.05). The W/D ratio (4.6 AE 0.6) and the serum levels of interleukin-8 (279 AE 46 pg/mL) and tumor necrosis factor-a (377 AE 59 pg/mL) in the CO group decreased significantly compared to the control group (5.8 AE 0.8, 456 AE 63 pg/mL, and 520 AE 91 pg/mL) (P < 0.05). In addition, CO inflation also significantly decreased malondialdehyde activity and apoptotic cells in grafts, and increased the superoxide dismutase content. Briefly, CO inflation in donor lungs in the setting of cold ischemia attenuated lung IRI and improved the graft function compared with oxygen.