Abstract Purpose Obstructive apnea is sometimes seen in patients with Beckwith-Wiedemann syndrome. The cause of apnea is not limited to macroglossia, and the surgical indication for obstructive apnea has not yet been established. The authors performed polysomnography for the assessment of apnea. Method Overnight polysomnograms were obtained in 2 patients who developed obstructive apnea after 1-stage repair for omphalocele. Case 1 Apnea index (AI), defined as apneic events per hour, indicated 17.3, and SpO 2 below 95% occupied 80% of the total sleep time. Computed tomography and magnetic resonance imaging indicated obstruction of the airway between macroglossia and the hypopharynx. Central tongue resection and the division of the frenulum linguae for associated ankyloglossia were performed 97 days after birth. One month after surgery, apneic events disappeared and SpO 2 below 95% occupied only 1% of the total sleep time. Case 2 Obstructive AI indicated 28.1. Division of the frenulum linguae and anterior glossopexy were performed 55 days after birth. Postoperative polysomnogram indicated a marked reduction of AI. Conclusions These results indicated that polysomnography was useful for evaluating obstructive apnea and that advancement of the tongue by division of the frenulum linguae may be recommended for the treatment of obstructive apnea in patients with Beckwith-Wiedemann syndrome.