Objective: The incidence of solid renal masses has increased sharply in recent years due to widespread use of abdominal imaging studies. The aim of the present study was to evaluate the incidence of benign lesions in solid renal masses according to tumor size. Materials and Methods:The authors retrospectively reviewed the records of 305 patients with 328 renal solid masses treated by surgery. Based on a report by one pathologist, the specimen tumor size and the histology of each lesion were tabulated. The frequency of renal cell carcinoma and benign renal lesions was evaluated and a correlation between tumor size and pathological features of the masses was observed. Results: The frequency of malignant lesions in the 328 renal masses was 83.2%. When lesions were stratified into groups with diameters ≤ 3 cm or > 3 cm, the incidence of benign histology was 22.9% and 13.3%, respectively (p = 0.026). The odds ratios for finding a benign lesion in masses ≤ 3 cm was 1.93 (IC 95%, 1.07 -3.46) compared to masses > 3 cm. Conclusion: The incidence of benign lesions is significantly higher in renal masses smaller than 3 cm in diameter, which should be taken in account when the treatment of renal solid masses is planned.