Résumé : The microstructure and mechanical properties of lattice structures of various relative densities manufactured by Electron Beam Melting were analyzed. Their microstructure was compared to that of bulk parts. Special interest was given to the effect of surface roughness on their elastic behavior. An efficient chemical etching post-treatment was performed on these structures. The elastic mechanical behavior of both as-built and etched structures was analyzed. Compression testing revealed that the important decrease in roughness caused by chemical etching results in an increase in relative stiffness, in comparison with an as-built structure of the same relative density.