Background The antioxidant properties of blood vessels contribute to their performance and patency of that vessel when used as a bypass conduit. Despite increased use of the radial artery (RA) in recent years, very little is known about its antioxidant properties. We compared the ability of the RA to generate superoxide and assessed its antioxidant protective capacity with that of the internal thoracic artery (ITA). Methods Vascular segments of the ITA and the RA were obtained from patients undergoing coronary artery bypass grafting (CABG) incubated in culture media for 2, 24, 48 and 72 hours. The amount of superoxide generated by each artery, and the deterioration of the endothelial function were assessed by using chemiluminescence (CL) and organ bath techniques. We also assessed the expression, localisation and the activity of superoxide dismutase ( SOD ) in both arteries; using reverse transcription-polymerase chain reaction (RT-PCR), immunolocalisation techniques and standard biochemical assessment of SOD activity. Results Under stress, the RA generated more superoxide (133.6 ± 54.7 at 72 h vs. 16.8 ± 6.4 at 2 h; P < 0.01) and its endothelial function deteriorated faster (56.3 ± 7.3 at 72 h vs. 20.2 ± 1.5 at 2 h; P < 0.0001) than that of ITA. Cu/Zn-SOD was found to be prevalent in the endothelium, while Ec-SOD was distributed evenly in the endothelium and media of both arteries. The activity of SOD was less in the RA compared with that of the ITA (510.2 ± 219.8 vs. 808.6 ± 343.7, respectively; P = 0.03). Conclusions Our study shows that the RA is less equipped with an antioxidant protective mechanism compared with the ITA. These findings could partially explain the differential clinical performance of these conduits in CABG.