Megadolichobasilarartery (MDB), i.e. the widened, elongated and tortuous course of the basilar artery, has been the topic of numerous publications; about 350 cases have been reported world-wide. It can cause many symptoms; isolated or combined cranial nerve lesions and ischemic or hemorrhagic changes are the most frequent. A hydrocephalus internus is a rare occurrence and many patients do not exhibit any symptoms. To date, angiography, computed tomography, and to an increasing extent magnetic resonance imaging (MRI) are the principal methods for diagnosis of MDB. Angiographic-like representations with CT and MRI are further developments which represent an alternative to angiography. With the help of special MRI sequences, furthermore, non-invasive CSF flow measurements for the etiologic evaluation of a hydrocephalus can be performed. For the example of a patient with MDB and hydrocephalus internus, the possibilities of modern imaging techniques are presented and discussed.