OBJECTIVE To elucidate whether a contrast agent dilution method (dilution method), in which gadoxetate disodium (Gd-EOB-DTPA) is diluted with saline, is useful for good-quality arterial-phase images. METHODS In this study we observed 494 hypervascular hepatocellular carcinomas (HCCs) in 327 patients with chronic liver disease. Three Gd-EOB-DTPA injection methods were adopted for comparison: 1) test injection method (undiluted Gd-EOB-DTPA and modified scan delay), in which a test dose of 0.5 mL of Gd-EOB-DTPA was injected to determine scan delay; 2) conventional method (undiluted Gd-EOB-DTPA and fixed scan delay); and (3) dilution method (diluted Gd-EOB-DTPA and fixed scan delay), in which Gd-EOB-DTPA was diluted to 20 mL with saline. Lesion-liver contrast was calculated. Image quality and lesion detectability were evaluated by two radiologists blinded to the injection methods. RESULTS The lesion-liver contrast of the dilution method was significantly higher than that of the other two methods. Lesion detectability of the conventional method (64%) was significantly lower than that of the other two methods (contrast agent dilution method, 95%; test injection method, 93%). The image quality of the contrast agent dilution method was significantly better than that of the other two methods. CONCLUSIONS The dilution method contributed to improved image quality, high lesion-liver contrast, and high lesion detectability in the arterial-phase images of GD-EOB-DTPA-enhanced MRI.