Cannabinoids (the active components of Cannabis/marijuana and their derivatives) are currently investigated as potential therapeutic agents in the treatment of different diseases, including cancer. Thus, today is well-established that cannabinoids exert palliative effects on some cancer-associated symptoms. In addition, evidences obtained during the last fifteen years support that these compounds reduce tumor growth in many different animal models of cancer. However, very few studies have been carried out to test the potential efficacy of these compounds in human cancer. The development of these studies is urgently required to investigate whether derivatives from marijuana are actually useful as anticancer agents. In the meantime these studies are completed (and standardized cannabis-based medicines are available in pharmacies), many patients are using cannabis extracts obtained from different sources as an alternative therapy to treat their cancers).