Nanosized cubic Y2O3 samples, undoped and doped with 10 mol% Nd2O3, Eu2O3, Gd2O3, Tb2O3, Ho2O3 and Er2O3 (Y(1.8)Ln(0.2)O(3), where Ln=Nd, Eu, Gd, Tb, Ho or Er), were prepared by means of a controlled hydrolysis method in an aqueous solution containing ammonia, Y(NO3)(3) and Ln(NO3)(3) as precursors, and a surface modifier. The microstrain and the average size of the diffraction domains have been calculated from the XRD patterns and the results have been compared with those obtained by a combustion synthesis. It is shown that the cell parameter of the C-M2O3 (bcc structure related to the CaF2 structure; the M atom is 6-coordinated) structure of doped Y2O3 is correlated to the ion size of the dopant. The shape of the crystallites appears to be needle-like in all cases, while the microstrains depend on the dopant and are probably due to surface effect. XRD and Raman analysis show that, despite the heavy doping, only one phase in the Y2O3 powders is present.