Objective To study the differences between renal clear cell renal cell carcinoma (CCRCC)and angiomyolipoma (AML)with minimal fat,whose size were both smaller than 3cm and the lesions center were both located outside the renal contour. Methods 6 cases of CCRCC and 18 cases of AML with minimal fat were analyzed retrospectively.All the lesions were confirmed pathologically.The morphological characteristics,plain and enhanced CT values were obtained for compare.Results The lesion length diameter,morphology,the early excretory phase CT value and the pattern of enhancement were not significant different between the two groups (P>0.05).There was significant difference in the focal cystic and necrotic between CCRCC group and AML group (P<0.05).Plain scan density,enhanced uniformity,pseudo capsule sign,plain CT values,medullary junction CT value and the pattern of enhancement from medullary junction phase were statistically different between those two groups (P< 0.001).Conclusion The focal cystic and necrotic,plain scan density, enhanced uniformity,pseudo capsule signs,plain CT values,the cortex and medullary junction CT value and the enhanced amplitude were very important role in differential diagnosis of CCRCC and AML with minimal fat.