Аннотация:The antioxidative activity of phosphonates bearing 2,6-di-tert-butylphenol or phenyl groups has been compared using DPPH test and in the study of the in vitro impact mitochondrial membrane lipid peroxidation. The results show that the activity depends strongly upon the presence of phenolic group but is improved by the influence of phosphonate fragment. It should be noted, that the most active compounds aganst Fe(3+)-induced peroxidation (5b, 7a and 7b) significantly decreased membrane potential of mitochondria and induced mitochondria swelling. At the same time active compounds 1, 2a and 6a did not influence the mitochondrial potential and swelling.