Mediastinal emphysema (pneumomediastinum) may result from lung disease, trauma, surgery, diagnostic or therapeutic procedure, but spontaneous occurrence is rare. Patients presenting with chest pain, radiating pain to neck and back, cough, dyspnea, dysphagia and demonstrate air-shadow line on left cardiac border by chest radiography. The authors' case is presented of pneumomediastinum, with subcutaneous emphysema occurring three days postoperatively, in a 12-year-old male patient who underwent bilateral vesico-urethral reimplantation under general anesthesia. The patient was treated conservatively with oxygen and had an uneventful recovery. The authors discuss the possible causes and its management with a review of the relevant literature.