Aim: To compare outcomes in patients treated with laparoscopic partial nephrectomy (LPN) and laparoscopic radical nephrectomy (LRN) for clinical T 1bN0M0 renal masses. Materials and Methods: Between 2002 and 2008, 33 and 52 consecutive patients who underwent LPN and LRN, respectively, for clinical stage T1bN0M0 tumors were retrospectively identified from a prospectively maintained database of 450 patients undergoing laparoscopic renal surgery. Perioperative, pathological, and postoperative outcomes were compared. Results: The two groups of patients were similar in age, sex, and body-mass index. Mean radiographic tumor size was smaller (4.8 vs. 5.2cm, p=0.04) in the LPN group. Mean operative time (228 vs. 175 minutes, p<0.0001) and mean estimated blood loss (233 vs. 112mL, p=0.003) were higher in the LPN group. Intraoperative complication rates of 15.2% versus 5.7% (p=0.28) and postoperative complication rates of 24.2% versus 13.5% (p=0.20) were observed in the LPN and LRN groups, respectively. Overall median follow-up was 15 and 21 months for the LPN and LRN cohorts, respectively. A 12.5% and 29.3% decline in estimated glomerular filtration rate was observed (p=0.002), and 30.3% compared with 55.7% of patients developed an estimated creatinine clearance (eCrCl) <60mL/minutes after treatment (p=0.04) for LPN and LRN, respectively. There were no differences in pathological stage distribution between the two groups. In the LPN group there were no local or systemic recurrences, and one positive surgical margin was observed. One patient developed metastatic disease in the LRN group. Conclusions: LPN for T 1b renal tumors provides superior intermediate-term preservation of renal function compared with LRN. Continued follow-up of these patients is required to evaluate oncological outcomes.