Terrorism is a serious threat and is also a huge challenge for Europe’s security. There is a constant development of forms and methods of attacks, there are also changes in the general profile of people joining terrorist activities. Religious motivation is the most important motivation when “becoming a terrorist”. It is noticeable mostly in radicalization of Muslims. Terrorist on a separatist basis is still present in Europe, however Islamic terrorism is governed by completely different plans, the goals and principles of attacks focus on the spectacular and as many victims as possible. The aim of the work is to identify the most important causes of terrorism that are associated with the attempt and classify them. It takes into account not only sources of terrorism, but also their interrelationships, factors affecting it, as well as changes occurring in the sphere of such phenomena.