The invention relates to a suspension of cerium oxide particles, of which the particles (secondary particles) have an average size of at most 200 nm, these secondary particles consisting of primary particles whose average size measured by TEM is of at most 150 nm with a standard deviation of at most 30% of the value of said average size, and for which the ratio of the average size measured by TEM to the average size measured by BET is at least 1.5. This suspension is prepared from a solution of a cerium III salt, comprising a colloidal dispersion of cerium IV, which is brought into contact, in the presence of nitrate ions and under an inert atmosphere, with a base； the medium obtained is subjected to a thermal treatment under an inert atmosphere and then acidified and washed. The suspension can be used for polishing.
