Cerebral atrophy is a common finding in elderly patients; however, cerebrovascular disease causing progressive focal cerebral atrophy and dysfunction is unusual. In this report, we present 3 cases of hemicerebral atrophy due to ipsilateral internal carotid artery (ICA) stenosis or occlusion mimicking neurodegenerative conditions. Patient 1 had a frontal dysexecutive syndrome potentially consistent with a diagnosis of behavioral variant frontotemporal dementia; however, neuroimaging revealed a chronically occluded left ICA and a pattern of atrophy restricted to the left middle cerebral artery territory, suggestive of a vascular etiology. Patient 2 presented with progressively worsening seizures and right-sided weakness consistent with left hemispheric dysfunction, with radiographic evidence of left hemicerebral atrophy. Angiography revealed a chronic dissection of the left ICA leading to left cerebral hypoperfusion. Patient 3 had asymmetric parkinsonism, alien limb, and cognitive impairment consistent with a diagnosis of corticobasal syndrome. His imaging, however, revealed atrophy and encephalomalacia within the anterior circulation watershed territories with chronic, severe stenosis of the left ICA suggestive of a chronic hypoperfused state. In this case series, we report 3 examples of hemicerebral atrophy secondary to chronic ipsilateral ICA vascular disease with diverse progressive clinical symptoms mimicking primary neurodegenerative conditions. This case series highlights the importance of considering chronic hypoperfusion and large-vessel severe stenosis or occlusion in patients with cognitive impairment and evidence of asymmetric brain atrophy. In addition to symptomatic treatment, the management of vascular risk factors including treatment with antiplatelet agents, statins, and revascularization procedures can be considered.