Density functional theory (B3LYP) is used to investigate the dependence of the properties of C4'-centered sugar radicals generated upon irradiation of DNA on the computational model. Calculations reveal that hydrogen hyperfine coupling constants (HFCCs) are independent of the model implemented. However, the HFCCs are highly dependent on the sugar conformation. Furthermore, the relative energy of conformers is highly dependent on the model system. Therefore, the model must be carefully chosen when studying the properties of these radicals. Our findings have important implications since numerous computational studies have used small models to investigate DNA radicals, and therefore may have produced unreliable results. (C) 2004 Elsevier B.V. All rights reserved.