The quality of welded joints depends on many factors. The relevant standards stipulate technical conditions of welds quality assessment, which provides the basis for stating whether the given joint is compatible with the requirements or whether it is defective. In practice, making welded joints that are totally devoid of defects is extremely difficult. To conduct the control of inner structure of the given joint a non-destructive method with the application of industrial CT scanner might be applied. This modern diagnosing method combines the x-ray examination with advanced computer technology. The basic advantage of computer-assisted tomography consists in examining objects in three dimensions and the possibility to carry out three-dimensional reconstructions. The aim of this article is to discuss the use of this method to evaluate the quality of welded joints made of aluminium alloys. Capabilities of computer-assisted tomography were depicted by the case of weld probes constructed with TIG (ang. Tungsten Inert Gas) welding by different process variables. One has made the analysis of the quality of probes showing the smallest and the biggest internal and external welding defects.