<p>The subject of the study was thin-walled composite columns with a closed cross-section. The aim of the research was to analyse the failure of compressed thin-walled sections with three cross-section shapes and four composite lay-ups. The study investigated the effects of column cross-section shape and composite lay-up on loss of load-carrying capacity. Experimental studies of the axial compression of thin-walled composite structures were conducted using interdisciplinary research methods, thereby determining, among other things, post-buckling equilibrium paths and modes of structural failure. In numerical simulations, the research was conducted using original finite element method models, including a failure model based on progressive failure analysis. The novelty of the present paper was the evaluation of the load capacity of profiles with closed sections, with particular attention to the influence of cross-section shape and composite-ply arrangement. The experimental and numerical results of the study were in quantitative and qualitative agreement.</p>