A control parameter is determined for a system for irradiating a predetermined target volume in a body with a particle beam. The system is constructed to direct the particle beam at a multiplicity of target points in the target volume in succession in order to produce at, each of the target points a predetermined dose distribution in a region around the target point. The control parameter controls the extent of an overlap of the dose distribution of a first target point with the dose distributions of neighboring target points. For determination of the control parameter, there is first determined a movement parameter which quantitatively characterizes the movement of the body at the first target point. The control parameter is determined in dependence on the movement parameter.
