We present an unusual case of simultaneous bilateral cerebellar infarction in the territory of the medial and intermediate branches of the posterior inferior cerebellar arteries (mPICA). The patient, a 57-yr-old woman, had no risk factors for cerebrovascular disease but a long-standing hypertension. Pathogenetic hypotheses of this unusual ischemic site of lesion may be referred to: A) two PICAs arising from an occluded basilar artery; B) both medial branches arising from the same PICA on one side; C) a haemodynamic mechanism with hypoperfusion in the most peripheral branches of the arteries; D) a double, simultaneous embolic stroke in mPICAs territory. Based on clinical course, supraortic duplex-scan, echocardiography, MRI, angioMRI and CT scans, and digital subtraction angiography, none of these hypotheses could be clearly associated with the pathogenesis of the lesion. Nevertheless, we propose that an anomalous common mPICA for both cerebellar territories should represent the necessary condition for the ischemic insult and, simultaneously, other factors should intervene as possible determining events.