The article concerns the effectiveness of sources of operational activities undertaken by one of the key institutions of the EU security system. Europol has been present in policing for over 15 years, but is still relatively unknown. The agency carries out tasks related to the prevention of cross-border threats, such as organized crime, terrorism and other forms of serious crime and related criminal offences. Europol’s operational activities are based mainly on criminal intelligence processes, including the collection, processing (analysis, evaluation, interpretation) and the exchange of information. In recent years there have been many changes in the activities of Europol. The most important occurred on 1 January 2010, when the legal framework of Europol was fundamentally transformed, which was a consequence of the change in its legal status. The change was important because the effectiveness of Europol in operating in a transnational dimension, particularly with regard to cooperation with other subjects of international law involved in fighting cross-border threats, depends on the possession of the appropriate legal status.The multiplicity of factors (such as political, legal, organizational) that shape the operational capacities of Europol means that they are one of the most debated aspects of the functioning of the institution. Reflections on the effectiveness of this institution are bold, if one takes into account that the evaluation of the effectiveness of the police formation is always a challenge for researchers. It should be noted that the discussion about the effectiveness of Europol’s operational activity alone may affect the accuracy of the final assessment of the agency.