OBJECTIVE: An investigation of incidences of nasal septal deviation (NSD) and its effect on surgical success in patients with congenital nasolacrimal dacryostenosis (CNLDO).METHODS: A retrospective review was made of the medical records of patients who presented to the ophthalmology clinic due to epiphora, were diagnosed with CNLDO and underwent probing. The diagnosis was established by history, clinical examination, and fluorescein disappearance test (FDT)1. Patients with FDT grade 2 and 3 underwent surgery. Success was defined as postoperative FDT grade 0–1. The patients were assessed in terms of gestational week, birth weight, type of delivery, nasal endoscopic examination findings (presence of NSD), time of surgery, treatments received, recurrence and complications.RESULTS: The study comprised 72 eyes of 58 patients who were diagnosed with CNLDO and underwent surgical treatment. Of the patients, 44 (75.86%) had unilateral, and 14 (24.14%) had bilateral CNLDO; 41 (56.94%) were female and 31 (43.06%) were male. The mean gestational age at birth was 38.01 weeks (32–41 weeks), the mean birth weight was 3321.25 (2020–4500 g), the number of cases delivered by cesarean section was 40 (55.56%), and 32 (44.44%) were vaginal deliveries. There were 13 (18.06%) patients with detected NSD after endonasal examination and 59 (81.94%) patients with normal endonasal examination in the Otorhinolaryngology (ORL) department. The time of surgery was 10 –34 months (mean: 19.06 months, SD: 5.73), the length of follow-up was 6–16 months (mean: 9.90 months, SD: 2.58). The rate of probing success was 80.6% (58 eyes), and there was recurrence in 19.4% (14 eyes).The success rate of the probing did not statistically significantly differ by gender (p=0.323), the mean birth week (p=0.123), the mean birth weight (p=0.186), the involved eye (p=0.891), the type of delivery (p=0.891), the mean length of follow-up (months) (p=0.701), the mean month of surgery (p=0.607), and the side of NSD (p=0.853). The incidence of NSD was statistically significantly higher in the group in which the probing failed, than in the group in which the probing was successful (p=0.004).CONCLUSION: NSD was identified in 18% of the patients who were diagnosed with CNLDO and underwent surgery. The incidence of NSD was significantly higher in the group where the probing procedure failed. Pre-treatment nasal endoscopy is important for the treatment planning and prognosis of CNLDO patients.