Laparoscopic partial nephrectomy (LPN) and radical nephrectomy (LRN) have been shown to be safe and effective treatment options for renal tumors. However, limited data are available regarding the long-term effect on postoperative renal function in patients undergoing LPN and LRN who have a normal preoperative serum creatinine (sCr) less than 1.5 mg/dL and a two-kidney system. We compared the long-term sCr in patients who were treated with LPN and LRN. From October 2002 to April 2006, a total of 93 and 171 patients with a single, unilateral, sporadic renal tumor, a normal contralateral kidney, and sCr less than 1.5 mg/dL underwent LPN and LRN, respectively. Perioperative, pathologic data and sCr at least 6 months after surgery were compared between the two groups. A total of 42 and 55 patients with at least 6 months of follow-up after LPN and LRN were evaluated. Tumors treated with LPN were significantly smaller (2.4 vs. 5.4 cm, P < 0.001) than those in the LRN group. The mean age, body mass index, gender, tumor location, and sCr (0.91 and 0.91 mg/dL, P = 0.93) were similar between the two groups. The mean operative time was longer for LPN (222 vs. 182 minutes, P = 0.002) with a mean warm ischemia time of 37 minutes (range 13–55). The mean 6-month sCr was significantly greater for patients undergoing LRN (1.4 vs. 1.0 mg/dL, P < 0.001). Similarly, a greater number of LRN patients developed renal insufficiency (sCr 1.5 mg/dL or greater) compared with LPN (36.4% vs. 0%, P < 0.001). Despite the warm ischemia and longer operative times, LPN preserves the kidney function better than LRN. In properly selected patients, LPN should be preferentially performed to prevent chronic renal insufficiency.