The invention provides a process for preparing organic nanoparticles comprising the steps of: (a) preparing a solution comprising an unsaturated polyester and/or a vinyl ester resin, an initiator and a hydrophobic monomer; (b) emulsifying the solution obtained in step (a) in an aqueous phase; and thereafter (c) curing the emulsified solution. The invention further provides organic nanoparticles obtainable by the process according to the invention; various uses of said nanoparticles; and paper, dye compositions and toner compositions comprising said nanoparticles.