Corticobasal syndrome is a neurodegeneration characterized by asymmetric parkinsonism, dystonia, myoclonus, and apraxia. In the early stage, CBS presents with asymmetric parkinsonism and cortical symptoms, and neuroimaging finding is often vague, making early clinical differentiation from idiopathic Parkinson disease challenging. This study was performed to delineate the specific patterns of cortical hypoperfusion, dopamine transporter uptake using dual-phase FP-CIT PET in discriminating between CBS and IPD at early stage.