Hemothorax is an exceptional, serious and misleading manifestation of extralobular sequestration. We report the case of a 15-year-old patient who consulted for chest pain and sudden onset dyspnea. The chest x-ray revealed fluid pleural effusion. Pleural puncture produced a bloody fluid and the angioscan showed a hyperdense formation without a systemic artery. Thoracotomy was performed. A left intrapleural pyramidal formation vascularized with a pedicle from the thoracic aorta was identified and sequestrectomy performed. At two years, the patient has remained symptom free. Extralobular sequestration is an exceptional cause of hemothorax. The absence of an aberrant systemic vessel on the angioscan should not rule out the diagnosis of sequestration. Precautions must be taken at surgery to avoid vessel damage.