Hemp (lat. Cannabis) is a plant whose use for medicinal purposes has been known for centuries. There are two species, Cannabis sativa and Cannabis indica. The first has long been used as a medicinal preparation for the treatment of many diseases. Due to its psychoactive effect, it was also used as a drug and was therefore on the list of substances whose use and sale is illegal. With the discovery of its active substances, the cannabinoids THC, CBD and CBN, research into their pharmacological effects as well as re-use for therapeutic purposes began. The active substances have an effect through the endocannabinoid system in humans. So far, numerous clinical studies have been conducted that have proven to have a positive effect in the treatment of neurological diseases, cancer and HIV / AIDS. Indications for use in these diseases have been approved and hemp and cannabinoid-based medicines have been registered. A problem in wider use is the side effects of these drugs as well as their dosage which is standardized, but the doses affect different patients differently and individual adjustment is necessary. The medical use of cannabis and cannabinoid-based drugs remains the subject of numerous clinical studies. There is therapeutic potential in a number of other diseases, but the results of effects in a large number of patients and dosing analysis are necessary to approve additional indications.