The two varieties of hemp, Cannabis sativa and Cannabis indica, contain about sixty compounds, named cannabinoids. The most abundant molecule, Delta9-tetrahydrocannabinol (THC), is involved in the biological effects of cannabis due to its analogy with endogenous substances (endocannabinoids) thus activating specific receptors : CB1 and CB2. A better knowledge of cannabinoids and their receptors leds to new interrogations, beyond the addictology, in particular in oncology. This review of the literature analyses these questions with special concern on the carcinogenic role of cannabis, the potential antitumor effect of cannabinoids and the place of THC and its derivatives for supportive care in cancerology.