ABSTRACT: The use of thin web/shell clay unit masonry is becoming increasingly widespread for its good thermal and acoustic insulation performances. However, clay units with thin webs/shells could be a source of weakness and brittleness when used in load-bearing masonry walls subjected to shear cyclic excitations. The aim of this research is therefore to study the applicability of such construction systems in moderate to medium seismic areas, evaluating their seismic performance through an experimental investigation followed by a numerical research. In this context, the paper will present the results of the in-plane test campaign on masonry piers representing three different masonry typologies, assembled using vertically hollowed clay units with thin webs and shell and tested under controlled boundary conditions, with different in-plane slenderness ratios and different applied vertical loads. The results are discussed in terms of in-plane failure modes, associated lateral strength and displacement capacity.