Pathological processes in the interpleural space appear on x-ray film as space-occupying growths. The assessment of such processes will always require x-ray films of the thoracic organs in two planes, rotating fluoroscopy and spot films as well as tomography. Additional information is obtained via oesophagus contrast radiography, angiography and mediastinoscopy. Computer tomography, being a non-invasive method, has proved very effective in such cases. Formation of an abscess in the mediastinum is rare, since the usually preceding mediastinitis is fatal even before an abscess is formed. In patients from countries where tuberculosis is still frequent, the possibility of formation of a cold abscess via liquafaction of specifically infected lymph nodes must be included in the differential diagnosis of mediastinal enlargement.