Security - intelligence services play an important role in the functioning of the state. Each country uses a variety of covert operations to protect its national interests. This work focuses on the Pakistan´s secret services whose actions have an essential role in the creation of domestic and foreign policy of Pakistan. Since their establishment in 1948, they receive assignment of keeping the national interests of Pakistan and throughout history we can find the ways in which they want to achieve their goals. One of these ways is the tactics of guerrilla war from which they spawned some of the most extreme Islamist parties. Considering that Pakistan is a land of economic, political and social instability, all this leads to a fertile ground for the development and activity of radical Islamist groups which have a significant impact on security and regional policy of Pakistan and the region in last few years. Inter - Services Intelligence (ISI) is a department within the military security - intelligence structure that is intertwined with the pakistan´s political structure. So we can connect ISI with examples such as the demolition of civil and the establishment of military government, political intimidation and examples such as corruption, smuggling, supporting Islamist parties and similar. All this brings us to the point where after 2001 Pakistan changed its policy to fight against terrorism. In that period ISI plays ambiguous role where on the one hand they support Islamic militants while on the other side they influence on development of Islamic fundamentalism and the uncertainty and instability in the state and environment.