Pneumomediastinum is a rare condition with an incidence of 1/33,000. It can be a rare complication of diabetic acidoketosis. We present the cases of two diabetic patients and review the literature, focusing our analysis on the interrelationships between these two diseases. Both patients were young subjects, a 21-year-old woman and an 18-year-old man with type 1 diabetes who were admitted for acidoketosis. Clinically, the patients presented the cardinal signs of diabetes and a flu-like syndrome associated with dyspnea and chest pain. Physical examination revealed a poor general health status, tachycardia and polymnea, as well as a painful diffuse tumefaction of the neck with subcutaneous emphysema. Blood tests disclosed elevated glycemia and urine was positive for acetone. The diagnosis of severe metabolic acidosis was retained. The chest x-ray demonstrated the subcutaneous emphysema and air in the anterior mediastinum. On the computed tomography scan obtained in the second patient, the heart was silhouetted with a hyperlucent zone laterally. Treatment consisted in strict bed rest with oxygen therapy, fluid replacement, insulin and heparin. The pneumomediastinum resolved in both patients within three days on average. The causal effect of diabetic acidoketosis in the development of pneumomediastinum in our two patients was retained after ruling out all other potential causes, including chest trauma and asthma.