In the World Anti-Doping Code and in the practice of its application in the sports world, four criteria were elaborated to guide the process of including new substances and methods on the Prohibited List, namely representing an actual or potential risk to the health of athletes, enhancing sport performance, violating the spirit of sports, masking the use of other prohibited substances or prohibited methods. However, these criteria do not fully address the question of how the selection should be carried out when a substance or method is included on the Prohibited List. The approach according to which the presence of any two out of the three following criteria — enhancing sport performance, representing a risk to the health of athletes, violating the spirit of sports — in a specific case can hardly be considered exhaustive and definite (the fourth criterion — masking the use of other prohibited substances or methods — is self-evident). The authors identify new problems that need to be taken into account in the future. These are, in particular, the need to improve the decision-making procedure for including new substances and methods on the List and to make it more transparent and the need to normatively settle the issue of using new technological devices, more specifically nanotechnologies and nanomaterials (technological doping).