PURPOSE: To evaluate US and CT characteristics of small renal cell carcinomas with diameter less than 3cm. MATERIALS AND METHODS: We retrospectively analysed US and CT findings of the small renal cell carcinomas which were surgically confirmed. We analysed echogenicity, peritumoral hypoechoic rim, intratumoral cysts on US. We analysed CT with viewpoints of tumor margin, growth pattern, renal contour change, attenuation on pre- and postcontrast scan, homogeneity, and perirenal changes. RESULTS: The US characteristics of the small renal cell carcinomas were hyperechogenicity(89%), peritumoral hypoechoic rim(66%) and intratumoral cysts(44%). They had relatively well-defined margin(90%), smooth and round contour(90%), endophytic growth pattern(65%), and outward bulging of renal contour(75%) on CT. They had iso- or high attenuation(87%) on precontrast CT, and were relatively homogeneous low-attenuated on postcontrast CT. CONCLUSION: The constellation of US and CT findings may be helpful in the diagnosis and understanding of the internal architecture of the small renal cell carcinomas.