Pneumomediastinum (also known as mediastinal emphysema) is defined as the presence of gas in the mediastinum. It can be spontaneous or arise as a result of trauma. Most cases can be effectively treated conservatively, however, if severe symptoms occur, cardiosurgical intervention is necessary. A Case Report: A man 20 years old, a victim of a traffic accident resulting in polytrauma, was transported to the Municipal Hospital of Jozef Strus in Poznan. Rapid tests performed at the Hospital's Emergency Room speeded up the diagnosis of a life-threatening pneumomediastinum. The patient was transferred to the Operating Room of the Cardiosurgical Department, where during an urgent surgery, the pericardial sac was decompressed. Subsequently, the patient underwent another surgery in the Thoracic surgery Department of the Wielkopolskie Center of Pulmonology and Thoracic Surgery. Afterwards, the patient had to spend a couple of weeks at the Intensive Care Department of Municipal Hospital of Jozef. Ultimately, after 6 weeks of hospitalization, the patient was discharged from the hospital in a good condition.Conclusions: The therapeutic success was an outcome of a quick diagnostic process, cooperation of doctors of various specialties and implementation of urgent surgical treatment. Mediastinal emphysema, which even though usually treated conservatively, may require lifesaving surgery in cardiothoracic surgery wards.