The paper describes the case of a 4-year-old boy with spontaneous pneumomediastinum secondary to a large bronchopneumonic focus, treated with supportive therapy including rest, painkillers, antibiotics and oxygen, which resolved in a short time with total remission of symptoms. Pneumomediastinum, also called mediastinal emphysema, identifies a clinical condition characterized by the presence of free air in the mediastinum and can be spontaneous or traumatic. Spontaneous pneumomediastinum is not associated with previous pathological events, such as trauma, endoscopic bronchial procedures, invasive ventilation and it is classified in primary and secondary to underlying disease. In 70-90% of cases it occurs in children with risk factors. Early diagnosis is critical for its management and, although the course of this disease is typically benign, hospitalization and observation are important because of possible significant and life-threatening complications.