INTRODUCTION: Renal masses are commonly managed by partial nephrectomy (PN) or active surveillance (AS). We assessed the impact of patient demographics and clinical indices in determining treatment decisions of renal masses between these two options. MATERIALS AND METHODS: We retrospectively reviewed our renal mass database to retrieve demographic and clinical records of patients who underwent immediate PN or entered a >= 12 month period of AS during February 1999 to May 2014. Age, gender, body mass index (BMI), Charlson Comorbidity Index (CCI) score, follow up time, tumor size, tumor location, renal invasion, creatinine, and estimated glomerular filtration rate (eGFR) were assessed as predictors of the selected treatment option. RESULTS: Seven hundred thirty-five patients with 744 renal masses underwent immediate PN, while 123 patients with 140 renal masses entered active surveillance. PN patients were predominantly male, younger, had elevated BMI, lower CCI scores, elevated eGFR and had larger tumors that invaded further into the renal collecting system. Renal masses in men were more likely to be treated by PN, while patients categorized as overweight or obese were 2-3 fold more likely to have their renal mass being manage by PN (versus patients with BMI in the normal range). Higher CCI scores were associated with a renal mass being more likely to be treated by AS, while increased renal mass size was associated with decisions to treat with PN. Compared to cortical location, renal masses abutting the renal collecting system were more likely to be treated by PN. CONCLUSIONS: Gender, BMI, CCI, tumor size, and tumor invasion into the renal system are useful predictors of renal mass treatment.