18 cases of benign intradural spinal cyst (9 arachnoidal, 2 neuroepithelial, 7 endodermal) are reported and compared with 94 cases (67 arachnoidal, 7 neuroepithelial, 20 endodermal) obtained from the literature. Arachnoidal intradural cysts (AIC) have no sex preference, occur at around the fourth-fifth decades of life and have characteristic intermittent root symptoms. They prefer the thoracic level and the posterior position. (Myelography images the cystic cavity (diverticular form). Surgical removal is usually easy. Neuroepithelial intradural cysts (NIC) are rare, have a 2:1 predilection for females and occur after the fourth decade. They have a serious clinical course similar to intramedullary or extramedullary tumours. They prefer the conus-cauda and the anterolateral positions. They often give rise to manometric block and to albuminocytological dissociation. There may be substantial adhesions to the cord and roots and the intramedullary variety presents no clear plane of cleavage. Endodermal intradural cysts (EIC) have a 2:1 predilection for males and prefer the second and third decades. They may have an intermittent or serious course with signs of root and cord impairment. They prefer the cervical segment (in the anterior position) and the conus-cauda (in the posterior position). As a rule they present manometric block and albuminocytological dissociation. Their frequent tough adhesions to the roots and cord demand special care during their removal.