This final paper analyses the torsion of thin-walled beams with circular and rectangular cross section, and the use of beams in exploitation, and described are advantages and disadvantages compared to beams with full section. The first part of this paper deals with the analysis of thin-walled beams with round cross-section, stress on certain parts of beams, possibilities of breaking-off, and appropriate design in order to avoid adverse consequences. Some examples for such beams, compared with beams with full rectangular cross section will be presented in this part of the final paper. The second part of this paper deals with the analysis of thin-walled beams with rectangular cross-section, stress, deformation and torsion. Examples of solved tasks for such beams are presented by comparing thin-walled beams and beams with full rectangular cross section. The last part of this paper compares the advantages of using certain types of beams in actual conditions, focusing on cost-effectiveness from point of view of the weight and permissible stress, as well as an example of stress calculation of thin-walled beams.