Ozonation can improve the properties of paper pulps. This is why the use of ozone is considered for improving recyclable paper pulps. Ozonation has no deinking effect. According to the composition of the recycled papers, it is possible to improve their mechanical or optical properties. It is difficult to foresee if these results will be significant from the technical and economical point of view because of the heterogeneity of the starting material. However, in certain cases, ozonation certainly is an alternative not to be neglected.