In principle, CBRN (Chemical, Biological, Radiological and Nuclear) materials or agents could potentially be used by terrorists to construct a weapon of mass destruction in the future. This is why the European Union (EU), IAEA, NATO and other international groupings or organizations have taken relevant measures in fighting this threat. At present, it seems that especially the high-activity radioactive sources used in industry and medicine present a potential danger which has to be addressed. At the international and national levels various measures have been introduced aimed at the reduction of the risk due to radiological terrorism, including prevention – ensuring that unauthorized access to such sources is as difficult as possible, detection – having the capability to detect radioactive materials if control over them is lost, and preparedness and response – being able to efficiently respond to incidents involving high-activity radioactive materials and recover from them as quickly as possible. Nevertheless, we have to be prepared for the use of radiological weapons and be able to realistically assess the danger they present and to mitigate their impact on the population and the environment. The paper discusses the real consequences of an attack based on a typical powerful radioactive source. It has been found that the impact would be much lower than usually predicted. However, one cannot estimate the chaos and psychological effects, which may be more dangerous than the exposure of persons affected and the radioactive contamination of the areas surrounding the site.

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