The case of a 34-year-old female patient come to the Emergency Department for neurological symptoms of recent onset is presented. No-contrast CT documented the presence of a neoformation approximately 3 cm in size in the 4th ventricle. For an in-depth diagnostic study of the lesion contrast enhanced MRI was performed. The examination detected a second minute (< 1cm) intraparenchymal nodule highly suspicious of metastasis from primary extra-cerebral neoplasm. The differential diagnosis of infratentorial lesions is discussed. It is concluded that the diagnostic combination of standard MRI with contrast sequences in the three conventional planes plays a major role in typing the nature of focal brain lesions.