Plasma sputtering deposition of Platinum thin films is studied on porous anodic aluminum oxide (AAO) template. The size effect of AAO cylindrical pores is shown to influence the diffusion of atoms in the porous layer. The resulting maximum reached depth of platinum varied from 2 μm to 20 μm, and the density on the surface is lowered from 23 μg.cm-2 to 5 μg.cm-2 as the pore diameter increased from 40 nm to 320 nm. The pore diameter is decreasing as Pt is deposited. Sputtered Pt is observed to grow as clusters on the surface and along the pore walls.