This study deals with the microstructure of a Pt modified aluminide coating obtained with an aluminizing treatment without prior Pt diffusion. IN100 (polycrystalline) and AM1 (single crystal) superalloys have been used as substrates and coated by an Aluminizing Phase Vapor Snecma (APVS(R)) low activity treatment developed by Snecma-Services. By using the Fisher experiment design method, we have shown that three types of microstructures can be obtained, depending on the type of the donor: a monophased (Ni, Pt)Al, a first two-phased PtAl 2 /NiAl, or a second two-phased PtAl 2 /NiAl with a continuous PtAl 2 layer. Moreover, the presence of platinum at the surface allows a better incorporation of aluminum by comparing the aluminizing treatment with prior Pt diffusion. Finally, stability of the newly observed two-phase structure PtAl 2 /NiAl with a continuous PtAl 2 layer at the surface has been investigated.