Lung herniation is defined as the protruding of the lung parenchyma outside the thoracic cage through a defect in the chest wall or diaphragm. A spontaneous posterolateral chest wall hernia is extremely rare. This report presents the case of a patient with chronic obstructive pulmonary disease who suffered from persistent cough and right back ecchymosis. The ecchymosis progressed and a protruding mass was noted the next day. Chest plain film and chest computed tomography revealed that the right lower lobe parenchyma had protruded from the thoracic wall. Conservative treatment was given and the lung hernia gradually regressed.