In this work nanometric spinel Co 1−x Cu x Fe 2 O 4 powders were obtained by polymeric precursors method at several annealing temperatures between 700 and 1200 • C. The samples were characterized by means of X-ray powder diffraction, confirming the ideal inverse spinel structure for CoFe 2 O 4 sample and the tetragonal distorted inverse spinel structure for CuFe 2 O 4 sample. Based on FWHM evaluation, we estimated that crystallite sizes varies between 27 and 37 nm for the non-substituted samples. The optical-active modes were determined by infrared and Raman spectroscopies. The phonon spectra showed a local tetragonal distortion for mixed samples.