From intra-arterial angiography studies and recently developed imaging techniques capable of non-invasively visualizing the flow territories of the cerebral arteries at brain tissue level, it is known that brain regions can be fed by multiple arteries simultaneously. This indicates a mixing of blood from separate supplying arteries before reaching the brain tissue. Herein, we aim to explore the various manners blood from different arteries may mix in both healthy individuals and in patients with steno-occlusive disease. Furthermore, the impact of cerebrovascular interventions on the blood flow patterns and its effect on the mixing of the blood supply is discussed. More accurate knowledge and understanding of the vascular sources of tissue perfusion, and potential mixing, may result in more efficient vascular therapies and interventions targeted specifically to affected brain tissue areas.