In recent years, evidence has accumulated to suggest that the endocannabinoid system, comprising the cannabinoid CB1 and CB2 receptors, their endogenous ligands anandamide and 2-arachidonoylglycerol, and their synthetic and degradative enzymes, plays a role in the pathogenesis and possible treatment of cancer types, including prostate cancer (for recent reviews, see [1]–[3]). This evidence concerns the gene CNR1 and cancer.