Varicella zoster virus (VZV) infection does not always provide lifelong immunity. A reinfection with VZV occurs more commonly than previously thought. Varicella infection spreads through the blood-stream, causing pneumonia. Varicella pneumonia results in bilateral pulmonary nodular infiltrations. We herein report a case of varicella reinfection with unilateral varicella pneumonia in which a reduced pulmonary blood flow due to radiation damage was considered to be the cause of unilateral pneumonia. In patients with an asymmetric pulmonary blood flow, careful interpretation of unilateral infiltration is therefore considered to be important with making a differential diagnosis.