Objective: The aim of this study was to evaluate the feasibility of low-concentration iso-osmolar Iodixanol 270 compared with Iohexol 350 in patients with coronary artery bypass grafts (CABGs) undergoing coronary computed tomographic angiography (CCTA). Methods: A total of 80 consecutive patients undergoing CABG follow-up with the use of CCTA were prospectively enrolled, with 40 patients assigned to Iodixanol 270 and 40 patients assigned to Iohexol 350. In both groups, the contrast medium was injected at an injection rate of 4.5 mL/s in the patients with a body mass index of greater than 24 kg/m(2) and 3.5 mL/s in the patients with a body mass index of 24 kg/m(2) or lower. The contrast volume was determined by the flow rate and scan time. Image quality score and visualization of bypass grafts were evaluated. Subjective assessment of image quality for each coronary artery segment was determined using a 4-point grading scale by 2 reviewers, whereas objective evaluation of image quality was conducted by measuring the mean CT attenuation values (hounsfield unit [HU]) in terms of SD, contrast-noise ratio, and signal-noise ratio in the ascending aorta. Results: The mean (SD) contrast volume for the Iodixanol 270 and Iohexol 350 groups was 66.28 (12.00) and 64.98 (8.12) mL, respectively, with no significant difference (P = 0.57). The mean (SD) CT attenuation value in the Iodixanol 270 group was 414.72 (101.47), which was lower than in the Iohexol 350 group, which was 478.85 (108.73) (P = 0.01). The subjective image quality for the Iodixanol 270 group was superior to that for the Iohexol 350 group in the arterial graft vessels (P = 0.027), whereas there was no significant difference between the 2 groups in the venous graft vessels (P = 0.377). There was no significant difference in terms of SD of the ascending aorta, signal-noise ratio, and contrast-noise ratio between the 2 groups. Conclusions: Low-concentration iso-osmolar Iodixanol 270 provides image quality comparable with that of Iohexol 350, allowing diagnostic CCTA follow-up of patients with CABGs.