Background/Aim: We investigated pre-operative factors for predicting whether renal masses are benign in order to facilitate the selection of optimal candidates for pre-operative biopsy. Patients and Methods: We evaluated 278 patients with renal masses suspected to be clinically T1 or T2 renal cell carcinoma. All patients had undergone a partial or radical nephrectomy. Pre-operative parameters, including patient characteristics, tumor size, and blood tests, were utilized to predict which lesions were benign. Results: Twenty-five lesions (9.0%) were benign. Multivariate analysis showed that female sex [odds ratio (OR)=2.92, p=0.016], serum albumin ≥4.3 g/dl (OR=3.50, p=0.013), and tumor size 23 mm (OR=3.96, p=0.002) were significant independent factors for benign renal masses. The incidence of benign lesions in cases with all three factors (female sex, higher serum albumin, and smaller tumor size) was 4 of 16 (25.0%), which was significantly higher (p=0.037) than that in all cases (25/278; 9.0%). Conclusion: Relatively high pre-operative serum albumin levels may be a predictor of benign lesions when associated with female sex and smaller tumor size.