When complying with anti-money laundering (AML) regulation, financial institutions faced some problems reflected in the form of risks and costs. In some cases, those problems have legal solutions but, in other cases, place banks in the position to decide between two risks – one being less harmful than the other. The aim of this dissertation is to provide an analysis of such risks and costs handled by financial entities, presenting some solutions provided by courts, but also identifying the gap between regulation and reality. Chapter I includes a general overview of money laundering; it makes reference to Financial Action Task recommendations in this matter and at the end the regulatory context of the crime in United Kingdom (UK). In Chapter II, each subsection refers to the risks banks may have when complying with money laundering regulations; the duality between the risk of being involved in a money laundering offence against the risk of being sued as a constructive trustee, the problem between reporting suspicious transactions against the tipping off offence, the dilemma of whether compliance with AML requirements and breaching contractual duties with customers, and an analysis of how legislation has partially solved the dilemma regarding confidentiality duty. Then, I shall discuss the costs that banks have to assume in implementing the AML system and the perception of the bankers regarding AML regulation.