AIM: Early identification of spontaneous pneumomediastinum can be recruited by thoracic ultrasound in emergency MATERIAL OF STUDY: A spontaneous pneumomediastinum in a 24 –year old man is reported RESULTS: The patient, who refused hospitalization, returned 12 hours later, complaining a massive subcutaneous emphysema, with a mild dyspnea. Thoracic CT confirmed suspected pneumomediastinum and the young man has been transferred to specialized DEA, with a good outcome by conservative treatment. DISCUSSION: Revaluation of the patient has been useful to critically analyze the unusual echographic report too. The major sensitivity and specificity of thoracic US, compared to conventional supine X-ray, is more and more appreciated, regarding occult pneumothoraces. Furthermore the recruitment of training to detect penumomediastinum is needed. CONCLUSIONS: Spontaneous pneumomediastinum is an extremely rare benign complications of chronic asthma in young population, caused by increased alveolar pressure, instrumental investigation may be supported by US in emergency too, associated to conventional X-ray and CT