Primary neoplasms of the central nervous system in children. Modern diagnostic imaging techniques are able to detect primary neoplasms of the central nervous system (CNS) in children safely and accurately but with less specificity as to cell type or degree of malignancy. These neoplasms, often peculiar in cell type and size, mediated by hydrocephalus in their clinical presentation, demand careful and often extensive imaging techniques best to evaluate their geography and character. Added to these basic observations, determination of the neoplasm from surrounding edema, detection of possible spread, and evaluation of residual or recurrent neoplasm are prime responsibilities of the pediatric neuroradiologist toward the child, neurosurgeon, and oncologist. 