PURPOSE: Our objective was to compare the effects of different iodine concentrations on characterizing small renal lesions. MATERIALS AND METHODS: Thirty-eight patients were enrolled in this study. All patients underwent an initial CT scan using 370 mgI/mL iodinated contrast media. Patients were then randomized into two groups for a follow-up CT. Group A (n = 19) received 250 mgI/mL iodinated contrast media, and group B (n = 19) received 300 mgI/mL contrast media. The mean Hounsfield units (HU values) of small renal lesions with a maximum size of less than 2 cm were calculated. Signal to noise ratios (SNR values) were likewise evaluated. Three uroradiologists assessed the lesion's conspicuity and the diagnostic influence of the artifact's proximity to the adjacent renal parenchyma. RESULTS: In group A, there were significant differences between the HU values of renal lesions and those of the adjacent renal parenchyma between the initial and follow-up CT. Conversely, in group B, there was no significant difference. Moreover, SNR values showed no statistically significant difference between both groups. Regarding lesion conspicuity, only one reader identified a significant difference (p = 0.032) in group A; whereas in group B, there was no statistical difference. The artifact's proximity to the adjacent renal parenchyma did not appear to have any diagnostic influence on differentiating the two (p < 0.05). CONCLUSION: In evaluating small renal lesions, 300 mgI/mL instead of 370 mgI/mL contrast media can be used; however, it is important to note that the use of 250 mgI/mL contrast media may reveal different results from that of 370 mgI/mL contrast media.