Numerous damages to cellular DNA are imposed by oxidative stress. Formation of stable products resulting from oxidation of nucleobases is one of many observed consequences. The oxidized species constitute a class of heterocyclic compounds with great diversities of physicochemical properties. Modified nucleosides significantly differ from their canonical protoplasts by tautomeric equilibriums, protolytic properties in the gas phase and water solution, they have altered oxidative susceptibility and N-glycosidic bond stabilities. However, what is most important, they have overwhelmingly altered pairing properties, which are directly responsible for observed cytotoxic properties of these lesions. Besides, since many analogues are structurally different with respect to canonical bases their presence in DNA must impose many energetic, structural and dynamic modifications. These aspect are reviewed as fruits of project no 39 supported by computational grant in Poznań Supercomputing and Networking Center (PSNC, Poland).