Computer tomography is much more clearly superior to cranial scintigraphy with regard to the identification and localization of pathologic infratentorial processes, than in the supratentorial range. 2. Computer tomography alone solves many diagnostic problems relating to the infratentorial range, but it cannot by any means solve all the problems. 3. The diagnosis identifying the kind of infratentorial growing and displacing tumors cannot be safely established either by computer tomography alone or by a combination of computer tomography and cranial scintigraphy. 4. Cranial scintigraphy and CSF scintigraphy can supply additional informations, support the diagnosis, or contribute towards establishing the final diagnosis, in cases where computer tomography alone supplies ambiguous, questionably positive or discrete answers. In such cases, the emphasis is on the etiologic grouping of unclear forms of hydrocephalos.