The case of a 66- year-old woman with coexisting idiopathic basal ganglia calcification(IBGC) and dementia was presented. The calcification was detected in bilateral basal ganglia, dentate nucleus, and thalamus by brain imaging. Serum calcium and phosphorus levels were normal. The underlying diseases of calcification of basal ganglia such as parathyroid dysfunction and other infectious, toxic, or metabolic illness were excluded. The patient had memory impairment and frontal executive dysfunction without aphasia, agnosia, apraxia, and visuospatial impairment in neuropsychological test. It suggested that the cognitive impairment might be due to the dysfunction of frontal-subcortical circuit.