The historical masonry walls are often characterized by different layers which can eventually be connected through transversal elements (diatoni). The structural behaviour of multi-leaf masonry panels is deeply influenced by the presence of these transversal connections, which can lead, or not, to a monolithic behaviour of the wall. Starting from the results of an in-situ test-campaign carried out by the authors in the past, comprised of 27 in-situ diagonal compression test, it has been possible to notice some discrepancies between the experimental results and the suggestions of Italian Technical Code, about the influence of transversal connections in multi-leaf masonry panels. Eight double-leaf masonry panels was been tested by diagonal compression to understand the role of transversal connection on shear strength. In this experimental tests the response of panels that was built with different leaf  materials was investigated. This aspect is also important to better understand the behaviour of diatoni in masonry wall.