Purpose: To compare the results of lacrimal syringing performed in clinical practice and under general anesthesia, and the clinical efficacy of lacrimal syringing under general anesthesia before endoscopic dacryocystorhinostomy and dacryoscintigraphy. Methods: The study included 148 eyes of 82 patients who underwent endoscopic dacryocystorhinostomy and silicone tube intubation from August 2018 to April 2019. The patients were examined with lacrimal syringing in clinical practice and re‐examined under general anesthesia. Based on the change in lacrimal syringing, the patients were assigned to inconsistent and consistent groups. The inconsistent group was subclassified into complete (‘regurgitation’ of lacrimal syringing changes to a ‘passage’ pattern) and partial improvement groups (the degree of regurgitation improves under general anesthesia). Results: Twenty (13.5%) eyes showed inconsistent results of lacrimal syringing performed in clinical practice and under general anesthesia; all showed improved passage under general anesthesia. The surgical results did not differ significantly (p = 0.336) between the consistent and inconsistent groups, but did between the complete and partial improvement groups (p < 0.01). Conclusions Lacrimal syringing under general anesthesia may enable an accurate preoperative diagnosis of the degree of obstruction. The combined results of dacryoscintigraphy and lacrimal syringing performed in clinical practice and under general anesthesia allow surgeons to evaluate the lacrimal drainage anatomy precisely and may be useful for predicting the functional success of endoscopic dacryocystorhinostomy.