A method for generating a robust radiotherapy treatment plan for a treatment volume of a subject. An adjusted voxel-specific dose objective is determined by “smearing” an initial voxel-specific dose objective a specified distance in at least one direction. A treatment plan based on such adjusted dose objective will be more robust with respect to setup uncertainties and organ movements. Smearing of the dose objective corresponds to adjusting the dose objective dose value of a voxel in accordance with dose objective dose values of voxels within the specified distance.