Recreational cannabis use in adults with epilepsy is widespread. The use of cannabis for medicinal purposes is also becoming more prevalent. For this purpose, various preparations of cannabis of varying strengths and content are being used. The recent changes in the legal environment have improved the availability of products with high cannabidiol (CBD) and low tetrahydrocannabinol (THC) concentrations. There is some anecdotal evidence of their potential efficacy, but the mechanisms of such action are not entirely clear. Some suspect an existence of synergy or “entourage effect” between CBD and THC. There is strong evidence that THC acts via the cannabinoid receptor CB1. The mechanism of action of CBD is less clear but is likely polypharmacological. The scientific data support the role of the endocannabinoid system in seizure generation, maintenance, and control in animal models of epilepsy.