Raman spectra in Sn1-xIrxO2 (x <= 0.15) nanocrystals were investigated to estimate and separate the contributions of phonon confinement and composition effects. To this end, the Raman frequency of the A(1g) bulk-mode of pure SnO2 and It-mixed nanocrystals has been studied in details as a function of the size and the Iridium concentration. As an initial working hypothesis it was assumed a linear dependence of the Raman shift as a function of the Iridium molar concentration, while a quadratic expansion of the dispersion curve has been utilised in the phonon confinement effect. Comparison of predicted and experimental results is reported. (C) 2010 Elsevier B.V. All rights reserved.