Purpose. To evaluate the anatomic effects of phacoemulsification on drainage angle status in primary angle closure glaucoma (PACG) using anterior segment optical coherence tomography (AS-OCT). Methods. A total of 62 eyes of 58 patients underwent cataract surgery in Farabi Rye Hospital, Tehran, Iran. Patients were examined postoperatively on day 1, week 1, and week 6. Indentation gonioscopy and AS-OCT were performed preoperatively and at 6 weeks after surgery. Main outcome measures were angle and anterior segment parameters by AS-OCT and amount of peripheral anterior synechiae (PAS) by gonioscopy. Thirty-five eyes had PAS =180 degrees (group 1) and 27 eyes had >180-degree synechial closure (group 2). Results. Mean age of the patients was 64.3±9.0 years. The mean extent of PAS was significantly reduced from 45.9 to 32.2 degrees (p<0.03) in group 1, and from 277.4 to 159.0 degrees (p<0.001) in group 2. Group 2 showed significantly greater reduction in PAS extent (p<0.001). Angle opening distance and trabecular-iris space area at 500 µm from the scleral spur measured by AS-OCT increased significantly in both groups (p<0.001 for both). Anterior chamber depth (ACD) increased and lens vault (LV) decreased after both procedures. However, the amount of change in ACD and LV and angle parameters were not significant between the 2 groups. Conclusions. Phacoemulsification resulted in opening of the drainage angle, deepening of the anterior chamber, and reduction of PAS extent in PACG eyes with or without extensive PAS. Greater reduction of PAS could be considered in eyes with PAS >180 degrees.