OBJECTIVE: To investigate the occurrence ratio, localization, and surgical outcomes of intraretinal cystic spaces in idiopathic epiretinal membranes (ERMs). METHODS: We retrospectively reviewed the charts of 432 eyes of 398 consecutive patients with idiopathic ERM who underwent vitrectomy and ERM peeling from January 2012 to September 2015. We selected cases with intraretinal cystic space prior to surgery, detected by spectral-domain optical coherence tomography. We then evaluated the effects of ERM peeling on intraretinal cystic spaces, best corrected visual acuity, and central retinal thickness at 6 months after surgery. RESULTS: Twenty-four eyes (5.5%) showed intraretinal cystic spaces before surgery, present in the inner retinal layer (the inner group) in 9 eyes, in the outer retinal layer (the outer group) in 6 eyes, and in both the inner and the outer retinal layers (the combined group) in 9 eyes. Additionally, 30 eyes with ERM but without any presence of intraretinal cystic space were selected randomly and classified as the no cyst group. At 6 months after surgery, the disappearance rate of cystic spaces was significantly greater for the outer group than for the inner group (83.3% and 11.1%, respectively, P = 0.011). The mean best corrected visual acuity improved significantly after surgery in the inner group, the outer group, and the no cyst group (P < 0.05 for all three groups) but did not improve in the combined group (P = 0.58). The mean central retinal thickness decreased significantly after surgery in the inner group, the combined group, and the no cyst group (P < 0.05). CONCLUSIONS: Intraretinal cystic spaces were observed in 5.5% of preoperative idiopathic ERM cases. Following surgery, the cystic spaces in the outer retinal layer disappeared at higher rates than those in the inner retinal layer, suggesting that the pathophysiologies of these cystic spaces are different.