From the material and geometric point of view, the thin-walled cold-formed profiles have specific specialties, which their design must responsibly take into account. In the terms of their resistance, an important issue is the effectiveness of mutual interaction between several webs. The local stability requirements related to unfavourable buckling effects of their compressed parts are very significant. Favourable effects, related to membrane stresses and post-critical behaviour are also important. Different calculation procedures with different results in the relevant standards and their confrontation with experimental results indicated the need for further investigation of post-critical behaviour of these members. The paper is divided into two parts. Part 1 presents fundamental information about experimentaltheoretical research oriented to determinate the resistance of thin-walled compressed steel members. The investigated members had closed cross-sections made from homogeneous materials. The theoretical analysis in this research is oriented to determinate the resistance of mentioned members according to European and Slovak standards, while the experimental investigation is to verify the theoretical results and to investigate the behaviour of mentioned members during the loading process. Part 2 will be focused on the numerical analysis of the results, as well as on the 3D-modelling and simulation of experimental tests.