A comparative study of the relative antioxidant activity (RAA) of fullerene С 60 and its amino acid derivatives is performed via amperometry and fluorimetry. The sizes of nanoparticles in the corresponding colloidal solutions are determined via dynamic light scattering (photon correlation spectroscopy) to study the effect the steric factors of the investigated compounds have on the magnitude of the RAA. Data are subjected to statistical correlation regression analysis using results obtained for the RAA dependence of fullerene С 60 and salt forms of its acid derivatives on the corresponding sizes of nanoparticles in colloidal aqueous solutions. A close negative (inverse) correlation is identified between the size of nanoparticles in a solution and their antioxidant properties, with a pronounced synergic effect related to the influence of both chemical structure of the studied compounds and their structural organization in colloid solution. It is found that the structure of a substituent in a molecule of amino acid derivative of fullerene С 60 also influences the size of the forming nanoparticles. At the same time, reductive properties of amino acid derivatives of fullerene С 60 are generally determined by the electron effects of substituents.