Introduction. Cannabis (also known as marijuana) is the most frequently used psychoactive substance in the world. The role of cannabis in medicine is rapidly evolving, and advances in the understanding of its pharmacology have led to numerous proposed uses of these drugs. State of the art. Cannabis contains Δ9-tetrahydrocannabinol and cannabidiol as the primary constituents responsible for pharmacological activity. It is now known that there are at least two types of cannabinoid receptors. CB1 receptors are found mainly in the CNS, and their primary role is to inhibit the release of neurotransmitters. CB2 receptors’ leading role is to modulate cytokine release and immune cell migration. Colocalisation of cannabinoid receptors with other types of nervous system receptors allows them to interact with many other transmitters such as dopamine, noradrenaline, acetylcholine, gamma-aminobutyric acid, serotonin, and glutamic and aspartic acids. Clinical implications. The rapidly expanding understanding regarding cannabinoids led to initial attempts to treat selected diseases with cannabinoid receptor agonists and antagonists. The most promising of these was the potential possibility of treating diseases for which current therapy is unsatisfactory, such as neurological diseases including multiple sclerosis, spastic muscular tension, extrapyramidal system diseases, neurodegenerative diseases and cerebral ischaemia. Attempts to treat psychiatric diseases (e.g. psychoses, neuroses, mood disorders, and alcohol dependence syndrome) with cannabinoids are much less advanced. Future directions. Cannabis and cannabinoids can be widely used to treat several diseases or alleviate symptoms, but their efficacy for specific indications is not always apparent. Further exploration is needed to understand whether the enhanced sensitivity to the cognitive effects of Δ9-THC depends on brain cannabinoid receptor dysfunction, and how these changes contribute to the cognitive deterioration and core pathophysiology symptoms associated with schizophrenia or other neurological and somatoform disorders.