Brain injury after aneurysmal subarachnoid hemorrhage (aSAH) has been linked to cerebral hypoperfusion in the acute and subacute disease stage. The areas most prone to hypoperfusion are the borderzone regions. In this study we obtained cerebral blood flow measurements in the subacute stage after aSAH, and longitudinal volumetric data. We found a moderate correlation between the ratio of borderzone/whole-brain perfusion and percentage brain volume loss. Thereby, perfusion in the watershed areas in the subacute stage could identify patients at a higher risk for future brain parenchymal volume loss. Consequently, increasing perfusion in these regions could be a future therapeutic target.