First experience is reported in the application of computerized tomography to tumorous diseases in childhood, being localized in the mediastinum, lungs, abdomen, bones and soft tissue. In the majority of cases the indication for CT was to identify or exclude tumors. In a little part the method served to determine the extent of the tumor for therapy planing. Despite the known difficulties in abdominal diagnosis encountered with computerized tomography a satisfactory result has been achieved by means of appropriate programs. There were difficulties in diagnosis of tumors in the small pelvic starting from the ovariens or the uterus and in diagnosis of recidivtumors. Using special possibilities of computerized tomography, e.g. measuring absorption values, the kind of disease can be diagnosed in some cases and specific therapeutical measures be planned. The limitations of this technic will be pointed out too.