Poisonous plants are a common cause of poisoning in humans. Poisoning can happen accidentally, usually by substituting edible plants for poisonous ones because they look similar. The toxicity of plants is related to the concentration of chemical substances such as alkaloids, glycosides, saponins and tannins. Alkaloids are natural organic compounds found in plants in the form of water-soluble salts. They are found in all parts of the plant but do not have to be equally present in all organs of the same plant. Glycosides are organic compounds that are widely distributed in plants and often give them colour, as many glycosides are plant pigments. They are found in underground and above-ground plant parts and are dissolved in the cell sap. Saponins are plant glycosides that form a soap-like foam in aqueous solution, cause haemolysis and can be very toxic. In plants they occur dissolved in the cell sap, mostly in underground organs. Tannins are high molecular weight phenolic compounds found in leaves, bark, fruits, wood and roots of plants. Inside the plant cell they are found in the vacuole. Great care should be taken when handling plants. Ingestion of poisonous plants leads to nausea, vomiting, abdominal pain, fever and possibly death. Besides ingestion, poisoning is also possible through direct contact with the plant and inhalation of pollen, resulting in allergic reactions and skin rashes. Furthermore, some plants are both medicine and poison, and the difference is in the dose. 22 poisonous plants from the area of Primorsko-goranska county are described and for each of the plants the Latin name, the active substances, the type of habitat in which it grows, the appearance and the toxicity are listed. To avoid the toxic effects of plants on our bodies, it is important to know how to recognise poisonous plants growing in our environment, which is helped by educating the general population from an early age.