A detailed low temperature scanning tunneling microscope investigation of the intramolecular conformations of individual porphyrin-based molecules adsorbed on different copper surfaces is presented. Depending on the substrate geometry, the molecules show different orientations on the surface and different internal configurations. While on the Cu(1 1 1) surface the molecule lies flat on the surface, on Cu(1 0 0) its legs are oriented nearly perpendicular to the substrate. On Cu(2 1 1) an intermediate situation takes place. The molecule lies flat on (1 1 1) nanofacets, but other configurations are found with one leg rotated out of the substrate plane. Accurate theory-experiment comparisons allow to precisely determine the conformation of the molecule in the different cases.