A 62-year-old man with a past history of sleep apnea syndrome, umbilical and left inguinal hernia repairs, was referred to the emergency room for acute respiratory distress. He had underwent a screening colonoscopy 12 h earlier for a family history of colonic adenoma. This colonoscopy was complete, normal, and uneventful.A plain chest X-ray showed a distended colon extending to the upper third of the right side of the chest (Fig. 1). Further anamnesis helped the patient to remember a right diaphragmatic hernia, well-documented by CT-scan years ago. He had not previously mentioned this condition, when evaluated for colon screening.The patient was admitted to the surgical intensive care unit. A CT-scan confirmed a right diaphragmatic hernia with terminal ileum and ascending colon content, no sign of mesenteric ischemia, and massive pulmonary collapse. Conservative treatment with nasogastric suction quickly improved the patient's condition. He was discharged at day-6. Diaphragmatic hernia repair was scheduled 10 weeks later. Laparoscopy showed a complete agenesis of the right diaphragmatic dome (Fig. 2; Fig. 3), and was therefore converted into laparotomy for complete surgical repair. Postoperative course was unremarkable. Patient was discharged on day-6. Follow-up at 1 month was uneventful.Congenital diaphragmatic hernias are rare and usually diagnosed in the pre- natal period or in neonates with respiratory distress, calling for emergency neonatal repair [1,2]. In underdiagnosed or neglecting adults, the condition can be life-threatening, as seen in our patient [3,4]. Surgical repair is therefore strongly recommended, even in asymptomatic patients [5]. Recurrences are exceptional.