Many defects in physiological processes are due to free radical damage. For example, reactive oxygen species, nitric oxide and hydroxyl radicals have been implicated in the parthenogenesis of cancer, diabetes mellitus, and rheumatoid arthritis. This work involved the characterization of phenyl-N-ter-butyl nitrone (PBN) type spin traps and compared the results with the more studied dimethyl-1-pyrroline-N-oxide (DMPO) type spin traps using the hydroxyl radical. Calculations were carried out at the density functional theory level (DFT). The energies of the optimized structures, hyperfine calculations in gaseous and aqueous phases of the spin traps and the hydroxyl radical adduct were calculated at the B3LYP correlation and at the 6-31G (d) and 6-311G (2df, p) basis sets respectively. The dielectric effect on the performance of the spin trap was determined using the polarized continuum model. The results show a localization of spin densities in both cases.