To compare positive surgical margin rates after robot-assisted and pure laparoscopic radical prostatectomy when neurovascular bundles are preserved, and to identify parameters affecting surgical margin status. From March 2004 to January 2009, 279 consecutive prostatectomies with preservation of neurovascular bundles were carried out by the same surgeon: 175 robot-assisted radical prostatectomies and 104 laparoscopic radical prostatectomies. An intraperitoneal Montsouris's technique was used for all cases. Patient's age, body mass index, prostate weight, prostate-specific antigen level, clinical stage, preoperative and postoperative Gleason score, percentage of positive biopsies, pathological stage, and positive surgical margin status were prospectively recorded in an institutional database. The two groups were retrospectively analyzed and compared. Positive surgical margin rates were 17% and 13% for the robot-assisted radical prostatectomy and laparoscopic radical prostatectomy group (P = 0.4), respectively. At multivariable analysis, only prostate-specific antigen level and prostate weight significantly affected the surgical margin status, where the type of procedure (robotic vs laparoscopic) did not have any effect. In our single-surgeon experience, prostate-specific antigen levels and prostate weight are predictive of positive surgical margin in patients undergoing nerve-sparing radical prostatectomy, whereas there seems to be no difference between the robot-assisted radical prostatectomy and the laparoscopic radical prostatectomy techniques.