Objective: To determine the feasibility of using contrast-enhanced abdominal CT to assess relative renal function. Materials and Methods: This retrospective study reviewed data from 32 patients who had had investigations by contrast-enhanced abdominal CT and 99mTc-MAG3 renal scintigraphy, within a period of not more than 30 days. Post-processing CT images of kidneys were by manual segmentation and calculated to interpret the relative renal function. Results: There was strong correlation between CT derived relative renal function and 99mTc-MAG3 renal scintigraphy (r = 0.971, p < 0.001) and no statistically significant difference in renal function between the two techniques (p = 0.572). Conclusion: Contrast-enhanced abdominal CT can determine relative renal function as accurately as renal scintigraphy. It is an appropriate alternative method, especially in hospitals where renal scintigraphy is not available.