The nanoparticles of Ni1-xCuxZn0.35Fe2O4 were synthesized by sol-gel method using polyvinyl alcohol as a chelating agent. X-ray diffraction patterns of all the samples confirmed the single phase spinel structure. The site occupancy of copper in the nanosized nickel-zinc ferrite spinels was investigated with the help of in-field Mossbauer spectroscopy. Cation distribution for the whole series of compositions was proposed by considering the amounts of iron ions present at both tetrahedral and octahedral interstitial sites in the spinel lattice. Confirmation of the proposed distributions was done by estimating quantitatively the lattice parameters for these compositions and comparing their values with those of the experimentally observed ones. (C) 2014 Published by Elsevier Ltd.