The subject of the invention comprises method of determination of distortion value and/or distortion correction value for a projection image obtained during computer tomography routine, with application, in particular, in control of the scanning process. The method is characterised in that during the first stage, during object scanning, the value of image distortion and/or its possible change present in individual projection images is determined, by determining the central point, namely the detector spot which receives the most intense irradiation from the X-ray source and/or by determination of calibration image and projection image parameter deviation and/or by comparison of projection images, including comparison of projection images with calibration images. The second stage includes an optional correction of projection image distortion, or when the distortion value exceeds the permitted limit during scanning, the scanning is automatically aborted, and the stage of projection image distortion correction ta
