The present invention relates to a catalyst which can be used in a process involving a conversion reaction for organic compounds, containing at least one support and at least one metal, and characterized in that it has particles of an average size greater than approximately 1 nm, and more than 80% of particles, the size of which is comprised in the range D±(D.0.2) where D represents the average size of the particles. It also relates to the process for preparing this catalyst which consists of preparing a colloidal suspension, in aqueous phase, of the metal oxide or metals to be supported, then depositing this suspension on a support, and optionally reducing the oxide thus supported.