Surface topography is a key element between process parameters and manufactured part performances. Within the context of 3D printed parts, one difficulty is to consider the total 3D surface topography including internal porosity. In this paper, an original method is proposed for the characterization of the surface topography, both internal and external. Starting from volumetric data obtained by Computed Tomography measurements, a method of surface extraction is performed that identifies skin voxels corresponding to the internal and external part surface,and which are the support to the calculation of the Specific Surface Area (SSA). A multi-scale analysis is thus proposed to characterize the total surface, (SSA), obtained at different scales. The interest of the multi-scale analysis is illustrated through various examples that attempt to link process parameters to part properties.