This case report describes difficulty with ventilation because of valve-like upper airway obstruction by aryepiglottic folds after uncomplicated insertion of a Combitube in a 30-year-old female patient. After correct (oesophageal) placement increased ventilation pressures occurred and a fibreoptic device was used to investigate the cause. Valve-like obstruction was discovered and subsequently observed during controlled ventilation. After removal of the Combitube and mask ventilation no valve mechanism was seen. This effect appeared to be due to an increased air stream caused by the obstruction of seven out of eight Combitube perforations.