Fused Filament Fabrication (FFF) is an additive manufacturing process based on the sequential deposition of fused filaments to construct 3D objects. While undoubtedly versatile, the process suffers from the presence, in the printed artefacts, of porosity defects that form networks whose features are directly related to the deposition direction [1]. The pores have characteristic size typically one order of magnitude smaller than that of the filaments, which becomes relevant when the printed artefacts have small dimensions, as in lattices, whose struts have often a thickness comparable with that of a filament. Experimental analyses on the tensile properties of struts made of parallel filaments have shown that the Young modulus is significantly sensitive to the width of the strut and that this sensitivity does not depend on the volume fraction of pores [2]. These results suggest that the behavior is not only governed by the properties of the deposited filament and the porosity content but also by a third phase constituted by the regions where two filaments interconnect [1]. In this work, first, an experiments-based micro-structural model of the elastic-plastic properties of this three-phase medium (filament, pores, interconnecting regions) will be presented. Then the model will be evaluated for the more complex system of three intersecting struts. The porosity network morphology is obtained from Computed Tomography scans for two different sizes of struts (and thus two different porosity networks). For this purpose, a dedicated elementary lattice specimen has been developed, which enables not only to perform CT scans but also to characterize the deformation and fracture mechanisms from in situ tomography mechanical testing. [1] A. Garg and A. Bhattacharya, An insight to the failure of FDM parts under tensile loading: finite element analysis and experimental study, Int J Mech Sci 120:225-236, 2017 [2] G. Simone, R. Manno, F. Barbe and I. Benedetti, Tensile failure of bio-inspired lattices with different base topologies, AIP Conference Proceedings, 2848 (1), 020019, June 2023 – https://doi.org/10.1063/5.0145012