Spontaneous dissecting aneurysms (SDAs) seldom involve the intradural vertebral artery VA, the posterior cerebral, basilar or postero inferior cerebellar arteries (PICAs), where they produce subarachnoid haemorrhage and/or ischaemia. These lesions may develop spontaneously or occasionally after minor trauma and occur in young people in whom there is no underlying abnormality to explain the appearance of the dissection in most cases. Spontaneous dissecting aneurysm of the PICA is rare and its natural history is not well understood. Surgery or endovascular treatment for PICA dissection remain controversial because they suggest vessel occlusion. Only in a few cases is the bypass between the occipital artery and the PICA possible with trapping of the dissected segment. Reinforcement of the arterial wall does not seem efficient and the surgical approach per se with sole exclusion of the aneurysm may be disastrous. We describe two cases of SDA of PICA that presented with subarachnoid haemorrhage (SAH), treated conservatively, with spontaneous cure of the lesions, angiographically confirmed at mid-time follow-up of five and four months. These favourable spontaneous thromboses, like 11 other similar case reported in the literature, did not show any rebleed. The possibility of a benign clinical course of this lesion exists; clinical and angiographic management of the patient before a decision for a aggressive treatment is proposed.