Cannabis is a plant that has been used for centuries to relieve a wide range of symptoms. Since the 1960s, interest in medical research into this plant has grown steadily. Already very popular for recreational use, a growing number of consumers not accustomed to using cannabis for psychoactive purposes have begun to use it as an alternative or complement to mainstream pharmaceutical medicines. The principal unsubstantiated or 'social' uses of cannabis are based mainly on data that is at best controversial, but usually not scientifically proven. The aim of this review was to identify the scientific basis and reasons that lead patients with cancer to consume cannabis, and also to identify whether there is a risk of interaction between cannabis and anticancer medicines through drug transporters (P-glycoprotein and other ATP-binding cassette superfamily members) Cytochromes P450 (3A, 1A, 2B, 2C, 2D families…) and glucuronyl transferases.