A 7-month-old infant with typical features of diencephalic syndrome (DES) associated with a hypothalamic mass, most probably a glioma, was treated with chemotherapy. The tumor showed clear shrinkage, but after more than 2 years regrowth was noted. During the treatment period the child regained normal growth and became free of symptoms. As radiation therapy, especially at a young age, has significant adverse effects and a neurosurgical approach to the diencephalic region also has the potential to cause significant sequelae, a chemotherapeutic option, when it exists, is preferred. Thus, in an infant in whom a glioma is suspected to be the cause of the DES, based on the clinical picture and the neuroimaging appearance, chemotherapy should be considered the primary therapeutic modality. Even if its effect is temporary, its use is well justified. The most appropriate treatment protocol still needs to be determined.