The EU's common counterterrorism policy as well as its active role in the fight against terrorism, has emerged as an answer to the more frequent high profile terrorist attacks and increased radicalisation. Even though, the EU has been faced with terrorist attacks since the 1960’s, these more recent events have created the perception of terrorism as the highest level security threat in the EU. This process has led to a rapid development of counterterrorism policy at the EU level. However, empirical research in this area remains sporadic and fragmented. The rationale of this research is to identify and analyse changes in the EU counterterrorism patterns based on the new findings, upgrade the existing corpus of empirical knowledge, examine and reassess theoretical concepts and finally contribute to the understanding of the EU security policy. The research is based on the qualitative content analysis of the EU official documents pertaining to the fight against terrorism. It is related to the EU counterterrorism policy in the period of January 1999 to June 2016. The methodology involves a process of identifying and coding key words, expressions and syntagmas for the purpose of abstraction and acquiring of categories and EU counterterrorism policy patterns. A corpus of 278 documents that shapes the fight against terrorism and the EU security policy was used as a representative sample and analysed further. This process was beneficial for explaining the ways in which the EU counterterrorism policy was formed, and it also provided possible answers for fighting these threats. NVivo software was used to support qualitative content analysis by assisting in organising and reporting on a substantive amount of empirical data. Results demonstrate that high profile attacks committed in USA in 2001, in Madrid and London in 2004 and 2005, and in Paris and Bruxelles in 2015 and 2016 have had a critical influence on the creation of three problem periods within which the EU counterterrorism policy has been institutionalised. The EU counterterrorism policy is being further enhanced and institutionalised after every high-profile terrorist attack. It has been demonstrated that new phenomena such as foreign fighters, terrorist organisations such as Al Qa'ida and ISIS, and irregular immigration on the EU borders also serve as catalysts of institutionalisation. Furthermore, certain endogenous factors like the EU open borders, economic growth, democracy, as well as the amplified use of internet, have additionally influenced the gradual institutionalisation of this policy. On the basis of the results, it could be argued that most threats identified in the documents are primarily associated with the Muslim society. Despite the fact the attacks were committed in a relatively small number of EU member states, they control and steer the fight against terrorism on the EU level. Findings in this research point to the fact that the EU counterterrorism policy has evolved gradually from using „soft“ towards “smart” or „hybrid“ power, which implies innovative combination of the elements of „soft“ and „hard“ power. However, it is not enough to observe the evolution of counterterrorism policy only in the spectrum of power. Results demonstrate how the Paris school concept of securitisation can be applied as this process rests on the mundane bureaucratic decisions of everyday politics that manifest itself by introducing new, restrictive measures as well as the instruments following high profile terrorist attacks. Although these preventative measures are directed towards further enhancement of security, they are relatively inadequately coordinated with the protection of the basic values upon which the EU was built. The analysis has demonstrated that in the areas of coordination, cooperation and integration, the EU has managed to impose itself as a significant actor, however the member states remain still polycentric, key actors regarding their national security. This research has been based on parameters, such as the number and categories of documents that have not been used in the existing research and studies so far. Also, the analysis included a recent period that was marked by rising radicalisation and the escalation of high profile terrorist attacks. The grounds for a thorough insight into the institutionalisation construction of the fight against terrorism has been created in the official EU documents. In conclusion, existing knowledge of the EU counterterrorism policy evolution has been broadened by the reassessment of the existing empirical studies and theories. This has enabled the understanding of the development, efficiency and future development patterns of the EU counterterrorism policy.