We discuss the case of a patient who presented with a bitemporal visual field disturbance thought to arise from chiasmatic compression secondary to a suprasellar mass. The patient was ultimately diagnosed with medulloblastoma with diffuse intraventricular disease. Careful review of magnetic resonance (MR) findings in this case demonstrate the apparent suprasellar mass to be within the suprachiasmatic recess of the third ventricle. The role of MR imaging in distinguishing between suprasellar disease involving the third ventricle and primary third ventricular lesions is discussed.