The cannabis plant and its derivatives have been exploited for centuries for recreational and medicinal purposes, with millions of regular users around the world. The recreational use of cannabis is reflective of its neuropsychiatric effects, such as anxiolysis and euphoria. However, cannabis appears to have an emerging therapeutic role, especially in chronic disease and as an adjunct to cancer treatment. Increasing evidence supports cannabis in the management of chemotherapy-induced nausea and vomiting (CINV) and for pain management; however, studies are limited, particularly by difficulties associated with standardized dosing estimates and inability to accurately assess biologic activities of compounds in cannabis and derivative products. Smoking cannabis has not been proved to be a risk factor in the development of lung cancer, but the data are limited by small studies, misclassification due to self-reporting of use, small numbers of heavy cannabis smokers, and confounding of the risk associated with known causative agents for lung cancer (such as parallel chronic tobacco use). Cannabis and its biologically effective derivatives warrant additional research, ideally, controlled trials in which the cannabidiol and the delta-9-tetrahydrocabinol strength and use are controlled and documented.