A 63-year-old man (case 1) was brought to our emergency unit following a high speed collision. He developed fatal cardiopulmonary arrest shortly after arrival despite resuscitation efforts. Tension pneumopericardium was revealed by chest X-ray and CT examination. An 18-year-old man (case 2) was admitted after a motorcycle accident. Pneumopericardium was noted on admission chest X-ray and CT examination. He developed cardiac tamponade after the examination. He was intubated and mechanically ventilated after the subxiphoid pericardial drainage. Pneumopericardium following blunt chest trauma is realized with tracheobronchial, pulmonary or esophageal injury. The clinical significance of pneumopericardium is the development of tension pneumopericardium resulting into cardiac tamponade. In a patient with traumatic pneumopericardium who requires mechanical ventilatory support, continuous pericardial drainage should be considered. In addition, tension pneumopericardium may occur in patients with breathing spontaneously as in our cases. In these cases, careful observation and immediate subxiphoid pericardial drainage are required.