The authors are surgeons of Moscati Hospital in Aversa (CE) – Italy, and one of them is a Radiologist in the same hospital; they describe a rare case of lumbar hernia, the Petit’s hernia and describe the anatomical aspects of parietals hernias. Subsequently they describe the diagnostics aspects and then the surgicals treatments. In this case-report the authors describe the surgical operation to use one prolene-net to close the parietal breach. The most important aspect, that the authors emphsasize, is the absolute importance of careful clinic examination to diagnose it. This work is completed with some pictures that show it; some pictures are made in operatory-room during the surgical treatment and some of them are TC images.