A method, a computation unit and a CT system are disclosed for reconstructing CT image data, which includes a plurality of image voxels, by way of a weighted filtered back-projection. To weight the projection data during the filtered back-projection, a weight function is used, which weights the projection data from central beams which strike a detector row relatively close to the edge of the row relatively less, and which weights the projection data of central beams, which strike a detector row more relatively centrally, relatively more.