Cerebral amyloid angiopathy (CAA), caused by amyloid beta depositions in the walls of small cerebral vessels, is remarkably common in the elderly. Its major clinical consequences include intracerebral hemorrhages (ICH) typically in lobar location, functional dependence (disability) and cognitive impairment. Cortical superficial siderosis (cSS) is a common finding in CAA patients and can even be the only magnetic resonance imaging sign of CAA. cSS is of high prognostic relevance regarding future intracerebral haemorrhage and disability. Previous studies suggest that cSS is caused by recurrent focal subarachnoid hemorrhages (fSAH). However, the exact mechanisms and the temporal dynamics of this highly relevant imaging finding are largely unknown. In addition to hemorrhagic manifestations, such as cSS, CAA patients also show ischemic lesions. Of particular interest are acute ischemic lesions as detected by diffusion imaging, which seem to be highly prevalent. Since haemorrhagic and ischemic lesions require fundamentally different therapeutic strategies, understanding the relevance and interplay of both lesion types is highly important for clinical decision making. The HIFI-CAA cohort study aims to provide novel insights into cSS, acute ischemic lesions and other relevant brain alterations in CAA through high-frequency (monthly) serial magnetic resonance imaging.