Reactions of reactive oxygen species, and more specifically, of hydroxyl radicals, with nucleotides, may lead to the generation of radicals in the base and the 2-deoxyribose moieties of DNA. In the present study, for the first time, emphasis was placed on the investigation of the possible reaction of 2'-deoxyadenosine-3',5'-diphosphate radicals, leading to the formation of the related 5',8-cyclo-2'-deoxynucleotide-3',5'-diphosphate. It has been shown by several authors that 5'R and 5'S diastereomers of the discussed molecule are formed with different frequencies in DNA. The 5'R form of 5',8-cyclo-2'-deoxyadenosine-3',5'-diphosphate was found to be the most stable one. Moreover, the investigated reaction paths have shown that the formation of the 5'R isomer is energetically favourable in both the aqueous and gaseous phases. Therefore, the presented results are in good agreement with experimental data.