Abstract Mediastinum is defined as the area demarcated by the thoracic inlet superiorly, the diphragm inferiorly, and the pleural cavities laterally. The mediastinum is a division of the thoracic cavity that contains thymus gland, the heart, trachea and portions of the seophagus, and other structures. Mediastinum divided into 3 region, anterior, posterior, superior, and middle regions. Pneumomediastinum or emphysematous mediastinum is existence of free air in the mediastinum due to spontaneous or secondary reasons. That can be confirmed with thorax X-Ray or CT- Scan thorax. The symptomps are severe central chest pain, shortness of breath, subcutaneous emphysema, laboured breathing and voice distortion. In physical diagnosis, especially on auscultation, there is spesific sign called “Hamman’s Crunch” (crunching sound corresponding with the cardiac cycle (Hamman’s Crunch). Pneumomediastinum can leadto pneumopericardium, pneumotoraks, penumoretroperitonium or penumoperitonium. Air in the mediastinal cavity can be absorbed by itself slowly, so penumomediastinum can treated non-operatively.