The structural and hyperfine properties of Cr-doped SnO2 nanoparticles are report in this work. X-ray diffraction patterns indicate the formation of only the tetragonal phase in samples with Cr content up to 10mol%. The presence of Cr ions drives to the particle size reduction. Mössbauer spectra are well-resolved by a distribution of quadrupole doublets. The solubility limit of the dopant is found to be at ∼3mol% Cr base on the quadrupole splitting evolution with the Cr content. The linear increase of the isomer shift as the Cr content is increased is assigned to a linear increase in the concentration of oxygen vacancies. © 2010 IOP Publishing Ltd.