Two adult domestic shorthair cats were examined because of pneumothorax. Neither had a history of trauma, and spontaneous pneumothorax secondary to small airway disease was diagnosed. In both cats, treatment consisted of thoracocentesis for evacuation of air and administration of anti-inflammatory agents. One cat had multiple episodes of pneumothorax and eventually died; the other had only a single episode of pneumothorax. Small airway disease should be considered as a potential underlying cause in cats that develop spontaneous pneumothorax. Additionally, the potential for pneumothorax should be considered in cats with small airway disease, particularly when clinical signs suddenly become much worse.