The electric dyadic Green’s function of integrated structures with High Impedance Ground Planes (HIGPs) is derived in this paper following a full-wave analysis in the spectral domain. The formulation proposed generalizes and contains as particular cases those ones for perfect (and not perfect) electric and perfect (and not perfect) magnetic ground planes and for inductive and capacitive metallic sheets, as well. Particularly, all these cases can be obtained by setting in the general expression of the spectral Green’s dyad elements the proper surface impedance associated to the speci­ c ground plane considered. Finally, some numerical results show the radiative capabilities of inductive/capacitive and high impedance ground planes acting as re®ectors for horizontal electrical sources.