At present, transnational organized criminals are involved in a wide-range of criminal activities. European Law Enforcement Agency EUROPOL is the most significant outcome of the internationalization of police cooperation in Europe and the European Union. Detecting criminal activities is one of EUROPOL priorities. During last 15 years Europol has gained a recognized experience in the field and now is delivering substantial operational support to national police forces of Member States. Within the framework of detecting criminal activities Europol, as a working method, applies the Intelligence Led Policing Concept to proactively exploit data gathered. In practice, Europol provides the 27 EU Member States with investigative links connected with various crime-related aspects. EUROPOL's contribution towards detecting criminal activities is a very complex issue. To give a general view on the importance of the subject, however, it is enough to describe tactical and organizational solutions, particularly in the field of combating Euro counterfeiting, criminal assets seizure and criminal intelligence, which form operational potential of EUROPOL. This article synthetically describes only selected solutions of EUROPOL's operational potential towards detecting criminal activities. All the operational aspects of Europol have been presented from police practice perspective. The article expresses only personal views of the author, which cannot be identified with those of the institution he is employed in. (Published Abstract)