In this final paper it is elaborated subject about free radicals. It is known that free radicals are compounds that have unpaired number of electrons and are neutralized with antioxidants. We distinguish natural and synthetic antioxidants, but we are primarly interested in natural antioxidants which are in our daily environment. Many of them are very common in herbs in the form of vitamins, amino acids, enzymes or hormones. Each of them in a specific way works with free radicals by immobilizing or removing them from our organism. That is the way they prevent development of deseases or unwanted conditions within the organism.But to know how vitamin E works or coenzyme Q10, which is just one of the antioxidants discussed in this paper, we must first become familiar with the nature of free radicals and how they are created. These chemical compounds called free radicals are characterized as short-living particles. They can occur in reactions with aclanes, alkenes, etc. As far as alkanes are concerned, the most common form of formation of free radicals is halogenation of alkanes.In this mechanism, the alkane atom reacts with hydrogen to form a free radical that continues the chain reaction and the end product the alkyl halide is formed. For alkene, the characteristic reaction of the formation of free radicals is the addition, which takes place in the presence of peroxide. Bromine and hydrogen are bonded to double bonds of alkene and free radicals are formed in intercourse. By studying the mechanisms in which free radicals are formed, it is concluded that the stability of free radicals follows the following sequence: tertiary ˃ secondary ˃ primary. Knowing the conditions that are needed for the reactions in which free radicals are formed, we now know which antioxidants can cure the creation of free radicals or remove them, which is why we often call them free radicals cleaners.