The aim of this study is to examine some key properties of medical polyurethane coatings on coronary stents such as thickness and size of pores on the surface of austenitic stainless steel (316L). Plates were used as carrier instead of real stents, because they are too expensive and difficult to work with. The carriers were dipped into the solution of polyurethane and tetrahydrofuran. Solutions of 1 to 5 wt % were prepared for the experiments and the numbers of the dipping were changed. The coatings were examined with Atomic Force Microscope (AFM). In contact mode detailed images with good contrast were made about the coatings. These images were processed with image processing algorithms in MATLAB and with the image analysis software belonging to the AFM instrument.