Increasing lines of evidence support an antitumourigenic effect of cannabinoids, including the cannabidiol (CBD) which does not posses the psychotropic effects of D9-tetrahydrocannabinol (THC). These include anti-proliferative and pro-apoptotic effects and they are known to interfere with several mechanisms in the tumorgenesis. Yet, evidence from clinical trials among cancer patients is needed. The aim of the current study is to evaluate the impact of CBD as single treatment among cancer patients.