Although the plant Cannabis sativa has been known for a long time as a medicine and today mostly as a recreational drug, only in the last few decades, with the discovery of the endocannabinoid system, the first scientific evidence was obtained of the pharmacological and physiological activity of its active compounds, phytocannabinoids. The endocannabinoid system is the name for a complex biological system, in the narrow sense, composed of two receptors, CB1 and CB2, and two endogenous ligands, the endocannabinoids AEA and 2-AG. The endocannabinoid system is involved in many processes, some of which are neurotransmitter regulation, immunomodulation, carcinogenesis and nociception. In addition to endocannabinoids, the endocannabinoid system can also be modulated by phytocannabinoids. To date, approximately 120 different phytocannabinoids have been recognized and isolated, whose in vitro and in vivo effects are often not predictable due to their complex relationship with the endocannabinoid system. Δ9-THC and CBD are the most studied phytocannabinoids and especially interesting because of their promising therapeutic possibilities.