Objective: The goals of this study were to evaluate the long-term results of endoscopic endonasal dacryocystorhinostomy (DCR) with or without a posterior mucosal flap and to compare the surgical success rates of that procedure in patients with a nasolacrimal duct obstruction.Patients And Methods: We retrospectively investigated the results of 78 endoscopic endonasal DCRs performed at the Baskent University, Department of Otolaryngology between December 2000 and March 2007 on 74 patients with a lacrimal obstruction. The patients were divided into two groups. During surgery, the posterior mucosal flap was preserved in 27 patients (group A) and removed in 47 patients (group B). All patients underwent intubation with a silicone tube at the conclusion of surgery. The silicone tube was removed within 6 months after surgery. The mean follow-up period was 36 months (range, 2-78 months). The results obtained were then compared.Results: Granulation tissue and synechia developed between the lateral nasal wall and the middle turbinate in one patient in group A (revision surgery was not required). In group B, granulation tissue at the rhinostomy opening was found in seven patients, and in four of those subjects, the granulation tissue obstructed the neo-ostium. These four patients underwent a second operation. In group B, synechia was noted between the middle turbinate and the lateral nasal wall in two of 47 patients. In group A, the procedure was successful for all patients except one in whom granulation tissue developed, and in group B, the surgical success rate was 88.3%.Conclusion: In endoscopic endonasal DCR, the closure of bare bone with a posteriorly based nasal mucosal flap that creates an anastomosis between the lacrimal sac mucosa and the nasal mucosa decreases the formation of granulation tissue. But, there is no significant difference of success rate between two groups.