Pneumomediastinum indicates the presence of air in the mediastinal space. It may be classified in three categories, based on the main causes of air dissection into the mediastinal structures: spontaneous pneumomediastinum (pnm), the most frequently encountered, post traumatic pnm and pnm secondary to non-traumatic rupture of an abdominal hollow viscus. This paper reports the experience of a major regional emergency surgery division in the management of pnm during a five years period. Physiopathologic correlations are discussed together with diagnostic and therapeutic options.