Introduction The negative influence of conversion from laparoscopic to open colorectal resection on early postoperative morbidity and outcome has been demonstrated several times. In this study, we analyzed the conversion rate and its influence on early postoperative morbidity and short-term oncological outcome following laparoscopic rectal resections. Methods From January 1998 to December 2006, 300 patients underwent laparoscopic resection due to rectal carcinoma at our institution. We compared the converted patient group with the non-converted patient group regarding demographical, clinical, surgical, and histological data, compounded with the early and late postoperative results. Results Two hundred seventy-four (91.3%) patients underwent laparoscopic rectal resection (LR) , while conversion resection (CR) was necessary in 26 cases (8.6%). Conversion rate was 13% during the first 100 resections and decreased to 3% during the last 100 procedures ( p  = 0.035). Male gender, higher body mass index, and presence of T4-tumor were risk factors for conversion. Early postoperative complications were more frequent in the CR group than in the LR group. Concerning local tumor recurrence and overall survival, there was no significant difference between both groups (local recurrence, CR at 3.8% vs. LR at 4.5% and overall survival rate, CR at 76.9% vs. LR at 89.1%) after a median follow-up period of 22.5 months. Conclusion Conversion to an open procedure during laparoscopic rectal resection correlates with an increased postoperative morbidity, however, without impairment of the short-term oncological outcome. The conversion rate is minimized by the growing experience of the operating surgeon and, therefore, is a marker of the learning curve.