We have developed a method that allows a systematic study of the ability of the Scanning Tunneling Microscope (STM) for imaging DNA. A drop of a solution containing the DNA is deposited on a conductive substrate. Then a mesh screening (mask) is placed on the sample followed by evaporation of a thin Platinum-Carbon film. The mask is removed after the evaporation. This exposes coated and uncoated DNA for examination. Metal-coated DNA can be identified unambigously by the STM and it is possible to find sections with both coated and uncoated regions. Our results show that the contrast given by uncoated DNA depends on the conductive substrate used. In the cases examined, our results suggest a strong tip-molecule interaction..