The article discusses the demands to be made on the various radiological methods in thoracic diagnostics in respect of their informative value for therapeutic consequences, as seen from the viewpoint of internal-cardiological intensive-care medicine. The importance of x-ray thoracic film in one or two planes is emphasised, with special reference to routine imaging. In consideration of the demonstration of essential pathological findings, routine chest x-ray film would be mandatory only the 40th year of age onwards and lateral projection from the 50th year. At any rate, about 50% of routine thorax x-rays in intensive-care wards show changes, the percentage being higher if there is a clinical suspicion of changes. Mention must be made of a so-called time phase lag between the x-ray thoracic findings and changed pulmonary arterial pressure. In diagnosis of pulmonary artery embolism the nuclear medicine methods are compared with pulmonary arterial angiography, taking sensitivity and specificity into account. 90% of pulmonary embolism show only non-specific changes in the chest x-ray. Together with these and perfusion scintigraphy a sensitivity of 98% can be attained, albeit with lower specificity, since perfusion angiography and angiography agree in only about 87% of the cases. The demands to be made on radiological diagnostics must be determined from case to case by the diagnostic effectivity in relation to the technical setup and cost. The cost aspect of the individual methods is of major importance when installing equipment in hospitals.