The thermal conductivity of sintered porous pastes of metals is modelled, based on an analytical and a numerical approach. The first method arises from the differential effective medium theory and considers the air voids as ellipsoidal pores of different sizes, while second one is based on the finite element method to analyse the scanning-electron-microscope images of the paste cross sections. It is shown that the predictions of both approaches are consistent to each other for a sample of porous silver paste. Pancake-shaped pores are the main sources of reduction of the thermal conductivity of porous pastes, and they block the thermal conducting pathways more efficiently than spherical and cigar-shaped pores. The decrease of the thermal conductivity of the matrix due to the presence of pores can be minimized with spherical pores. The predictions of the proposed methodology could provide useful insights on the thermal behaviour of porous pastes.