We demonstrate here for the first time the relationship between electron work function of metallic substrate material, used for coating with thin dielectric carbon (DC) film, and surface thrombocompatybility of this structure. Thin dielectric layers of DC, with thickness below 1 microm, were deposited on medical steel 316L, titanium alloy Ti6Al4V and titanium nitride (TiN) using the RFCVD method. The values of the DC coated metallic electrode potential in water and in serum and the number of adhered blood platelets to the DC coated metals depended on the electron work function (phiM) of the metallic substrate. As the phiM increased, the electrode potentials increased, whereas the number of adhered blood platelets decreased. This effect permits controlling the interaction between blood and the thin DC films by selecting an appropriate metallic substrate.