The last decade has seen the emergence of new internet technologies that have acted as important facilitators of online drug markets. The internet now hosts a range of virtual marketplaces (both on the surface and deep web) for selling and buying illicit substances, as well as representing a new arena for health and law enforcement interventions. This first EMCDDA investigation into the world of online drug markets brings together state-of-the-art input from over 20 experts — from academia, journalism and frontline practice — and contributes to the knowledge base on this part of the supply chain