Reversible cerebral vasoconstriction syndrome(RCVS)is a clinical and radiological syndrome that is characterized by recurrent severe thunderclap headaches with or without other neurological symptoms and diffuse segmental constriction of cerebral arteries that usually resolves spontaneously within three months. Posterior reversible encephalopathy syndrome(PRES)is also a clinical and radiological syndrome characterized by headache, seizures, altered consciousness, cortical blindness, other focal neurological signs, and a diagnostic imaging picture of brain vasogenic edema. Both syndromes can occur in similar clinical contexts such as hypertension, pre-eclampsia/eclampsia, drug neurotoxicity, uremia, and some autoimmune diseases, and are frequently associated. Although the syndromes are usually fully reversible with early diagnosis and prompt treatment, some cases can develop hemorrhagic or ischemic brain lesions, often resulting in permanent disability. We need to be aware of the typical and atypical imaging manifestations of the syndromes to make an accurate diagnosis.