The purpose of this study was to evaluate the role of vitrectomy with cystotomy in the treatment of diabetic cystoid macular edema (CME). Among 22 eyes of 21 patients with diabetic CME underwent phacoemulsification, intraocular lens implantation, pars plana vitrectomy, induction of posterior vitreous detachment, and cystotomy or cystectomy. Follow-up ranged from 3 to 29 months. Under biomicroscopic examination, Cystoid macular edema was eliminated in 16 of 22 eyes during the follow-up period. Ring-shaped residual edema was observed in one eye. Corrected visual acuity improved in 7 of 22 eyes by more than one Snellen line (P = 0.0391, paired t-test), remained the same in 13 eyes, and decreased by more than one line in 2 eyes. This pilot study shows that cystotomy may have a role in the treatment of cystoid macular edema in diabetic patients.