This dataset contains X-ray measurements of a walnut obtained using the cone beam CT scanner in the Industrial Mathematics Computed Tomography Laboratory at the University of Helsinki. The measurements were made on 11 November 2020. The file 20201111_walnut_raw_data.zip contains 721 X-ray projections in .tif format from this measurement. The images have been post-processed to compensate for dark current and flat-field non-idealities, but no other modifications have been made. The package also contains the metadata file for the scan parameters. The center of rotation does not lie in the center of the projections, and making this assumption will lead to artefacts in the reconstruction. It was estimated that the best correction for this can be obtained by circularly shifting the projections left by 5 pixels before making any other computations. The file 202011111_walnut_sinograms.zip contains 2D fan beam sinograms constructed from the center plane of the cone beam. These are available in various resolutions obtained by binning of the raw data by factors of 1, 2, 4, 8, 16, and 32. The data is stored in MATLAB .mat files. The relevant geometric parameters of the fan beam are also stored in the .mat files. The sinograms have been pre-corrected for the incorrect center of rotation.