Pneumatocele and haemato-pneumatocele are air or air/fluid cavitary lesions which develop in the lung parenchyma after thoracic trauma. The formation of this lesion requires a direct violent impact on the pliable lung wall which explains its frequency in young adults. They are preferentially localised in the lung bases. The importance of associated lesions often marks the pneumatocele. Though rarely described, its frequency is certainly underestimated. If haemoptysis is the most frequent clinical sign it is the chest x-ray which demonstrates the early abnormality in the form of a rounded translucent image with a fine contour and variable diameter. The existence of a fluid level suggests the presence of blood (haemato-pneumatocele). The differential diagnosis with a localised pneumothorax, a diaphragmatic hernia and a pre-existing cystic lesion is easy as a rule but an evacuated pulmonary haematoma may lead to the discussion, especially as the mechanism of their formation may be the same. In isolation their clinical implications are minimal, their evolution favourable and after several weeks with a restitution of the integrity of the pulmonary parenchyma the absence of therapeutic intervention is justified.