To investigate the relationship between the size of macular holes and the possible benefit of internal limiting membrane (ILM) peeling. 84 consecutive cases of idiopathic macular hole followed up for at least 3 months were included in this retrospective study. Surgery comprised pars plana vitrectomy, peeling of any epiretinal membrane, 17% C2F6 (hexafluoroethane) gas filling and 10 days of positioning. 36 eyes had ILM peeling. The main outcome measure was the macular hole closure rate checked by optical coherence tomography. The overall postoperative closure rate was 90.5%. For macular holes > or =400 microm in diameter, the rate was 100% with ILM peeling versus 73.3% without (p = 0.015). For smaller macular holes, the rates were 100% in both groups. Postoperative gain in visual acuity was not significantly different in eyes with ILM peeling and those without. ILM peeling does not seem to be useful for macular hole <400 mum in diameter. Its likely benefit has to be investigated for larger macular hole sizes, for which the failure rate is higher.