Starting from the observation of a case of late diagnosed leftside hernia after traumatic rupture of diaphragma, the authors consider the increasing incidence of this patology during the years. The increased frequency of thoraco-abdominal traumas and the more sophisticated diagnostic tools, permit an earlier diagnosis nowadays. In our patient the diagnosis was made late on the basis of the standard x-ray of the thorax. The CT scan of the thorax and of the abdomen gave more information. Left thoracotomy enabled a wide exposure of the herniated viscera; the breakthrough of the diaphragm was repaired by means of interrupted suture and it was necessary to apply two prostheses of synthetic material.