AIM: To compare the outcomes of Ex-PRESS implantation in one eye versus trabeculectomy with mitomycin C in the fellow eye in Chinese patients with primary open-angle glaucoma (POAG). METHODS: This was a prospective, non-randomized comparative study. Forty-eight eyes of 24 patients with bilateral POAG necessitating surgery were included and underwent Ex-PRESS implantation under the scleral flap in one eye and trabeculectomy in the other eye according to patients’ choice. Primary outcome measures included mean intraocular pressure (IOP) and success rate. Secondary outcome measures were aqueous flare, postoperative medication use, visual acuity, and incidence of complications. RESULTS: All 24 patients finished a 1-year follow-up. Both groups maintained significant reductions in IOP after surgery throughout the follow-up period. At any point in time, the IOP of the two groups did not differ significantly. The Kaplan-Meier survival curve analysis showed no significant differences in success between the two groups (P=0.289). The mean number of anti-glaucoma medicines and visual acuity in both groups were not significantly different. Eyes with Ex-PRESS implantation had lower aqueous flare values on days 1 and 3 (both P<0.05). Instances of early postoperative hypotony and choroidal effusion were significantly fewer in frequency after Ex-PRESS implantation under the scleral flap compared with those after trabeculectomy (P<0.001). CONCLUSION: Ex-PRESS is comparable to trabeculectomy in terms of IOP, success rate, number of glaucoma medications used, and visual acuity. However, Ex-PRESS resulted in fewer cases of in?ammation and a lower rate of complications.