Apparatus for determining an actual effective radiation dose distribution in the case of irradiation of a moving target volume which has a plurality of volume elements, having the following features: a device for detecting first positions of the plurality of volume elements in a first motional state of the moving target volume; a device for detecting further positions of the plurality of volume elements in at least one further motional state of the moving target volume; a device for determining transformation parameters by means of transformation of the first positions into the further positions; a device for irradiating the moving target volume in accordance with an irradiation plan having a plurality of raster points to be irradiated, wherein the irradiating device is further arranged to detect, during the irradiation of a raster point, which of the motional states is occupied by the moving target volume; a device for assigning raster points, during the irradiation of which the moving target volume occupied the first motional state, to a first sub-irradiation plan; a device for assigning raster points, during the irradiation of which the moving target volume occupied the at least one further motional state, to at least one further sub-irradiation plan; and a device for determining the actual effective dose for at least one of the plurality of volume elements, in each case from contributions from the raster points (222, 222a) of the first sub-irradiation plan and of the at least one further subirradiation plan, using the transformation parameters, characterized in that the contributions from the raster points (222, 222a) in each case include parameters for calculation of an absorbed radiation dose and a relative effectiveness. a device for detecting first positions of the plurality of volume elements in a first motional state of the moving target volume; a device for detecting further positions of the plurality of volume elements in at least one further motional state of the moving target volume; a device for determining transformation parameters by means of transformation of the first positions into the further positions; a device for irradiating the moving target volume in accordance with an irradiation plan having a plurality of raster points to be irradiated, wherein the irradiating device is further arranged to detect, during the irradiation of a raster point, which of the motional states is occupied by the moving target volume; a device for assigning raster points, during the irradiation of which the moving target volume occupied the first motional state, to a first sub-irradiation plan; a device for assigning raster points, during the irradiation of which the moving target volume occupied the at least one further motional state, to at least one further sub-irradiation plan; and a device for determining the actual effective dose for at least one of the plurality of volume elements, in each case from contributions from the raster points (222, 222a) of the first sub-irradiation plan and of the at least one further subirradiation plan, using the transformation parameters, characterized in that the contributions from the raster points (222, 222a) in each case include parameters for calculation of an absorbed radiation dose and a relative effectiveness.