Unilateral Pulmonary Artery Agenesis (UPAA) is a rare congenital anomaly during the 4 th week of gestational age. It is defined as an absence of pulmonary parenchyma and its supporting artery. A 9-year-old girl was admitted to our hospital because of chronic cough. Chest examination showed a decrement in lung sound of right hemi-thorax with expiratory wheeze. Chest radiography (CXR) revealed a semi-opaque right hemi-thorax. Chest CT with intra-venous contrast demonstrated absence of the right pulmonary artery and lung parenchyma with hyper-inflated left lung and dextro-position of mediastinum. This case emphasizes that in patients with respiratory compliant and chronic cough CXR must be done to rule out similar diagnosis other than asthma.