An 89-year-old patient was admitted to the emergency department (ED) because of sudden onset of chest pain. The chest radiograph appeared to show a detachment of the pleura on the right side. The diagnosis of a pneumothorax was made. Insertion of a chest tube was indicated, but the patient refused her consent. The next day, another chest radiograph was taken. It showed no more detachment of the pleura. The initial diagnosis of pneumothorax had to be abandoned as retrospectively the pneumothorax could be identified as an artefact. Different aspects of pseudopneumothorax are discussed.