Water solutions of starlike hexaanionic fullerene derivatives, C-60[(CH2)(4)SO3Na](6) (star-ionomer) consisting of a C-60 cage covalently bonded with six ionic sulfonate arms, were studied using small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS). Nearly monodisperse aggregates of the novel star-ionomers were observed in the solutions of concentrations from 4% down to 0.5%. The structure of the spherical-like aggregates bears high similarity in different concentrations studied. Information regarding the aggregation number, hydration number, size, and shape of the aggregates was obtained from a combined analysis of the SANS and SAXS data.