The influence of Sn in Fe2O3 thin films is addressed. The presence of the tin ions decreases the Fe2O3 particle sizes and surface roughness decreasing of the films' surface is observed as a consequence. X-ray diffraction and atomic force microscopy measurements together with literature results support this phenomenon to be related to the segregation of the additive onto the surface and consequently surface energy decrease, which constitutes the driving force for the microstructure modification, similarly to results previously obtained for powders with same compositions. The effect of the anions introduced in the system as counter-ions of the precursors is also discussed.