BackgroundThe lymph node ratio (LNR; number of positive nodes divided by total nodes harvested) has been demonstrated to be a prognostic factor in colon cancer, but its role in extraperitoneal rectal cancer is still debated; furthermore, no data are available on laparoscopic rectal resection. The aim of this study was to evaluate the prognostic impact of LNR on long-term outcomes after laparoscopic total mesorectal excision (LTME) for extraperitoneal cancer in consecutive patients with a 5-year minimum follow-up. Methods This study is a prospective analysis of consecutive patients who underwent LTME for adenocarcinoma of the extraperitoneal rectum. Results LTME was performed in 158 patients. The median number of LN harvested was 12 (range = 3-25). The proportion of specimens with fewer than 12 examined LN was significantly higher in patients who had neoadjuvant chemoradiotherapy (p < 0.001). During a median follow-up period of 122 months, the local recurrence rate was 8 %. At univariate analysis, disease-free survival and overall survival significantly decreased with increasing LNR (p < 0.001). Multivariate analysis showed that the distal margin ≤1 cm was the only independent predictor of local recurrence (p = 0.028). LNR (cutoff value = 0.25) and lymphovascular invasion were significant prognostic factors for both disease-free (p = 0.015 and p = 0.046, respectively) and overall survival (p = 0.031 and p = 0.040, respectively). Even in the subgroup of patients in whom fewer than 12 LN were examined, LNR confirmed its prognostic role, with a statistical trend toward worse disease-free survival and overall survival. Conclusion Metastatic LNR is an independent prognostic factor for disease-free survival and overall survival after LTME for extraperitoneal rectal cancer. Keywords Lymph node ratio Survival Laparoscopy Total mesorectal excision Rectal cancer Excellence of surgical technique is of particular relevance in the treatment of extraperitoneal rectal cancer. Routine excision of the intact mesorectum during resection of cancer of the middle and lower rectum has resulted in a significant decrease in local recurrence rates [1]. Developed and popularized by Heald and co worker [1], total mesorectal excision (TME) is presently the surgical gold standard, with a 4 % local recurrence rate and a 78 % tumor-free survival rate in curative cases at 5 years [2]. A recent meta-analysis by Huang et al. [3] of randomized controlled trials that included small numbers of patients with upper or mid-to-low rectal cancer did not show differences between laparoscopic and open surgery in terms of the number of lymph nodes (LN) harvested, local recurrence, 3-year disease-free survival, and overall survival. Although a minimum of 12 LN in the