A turbine stator vane for use in a gas turbine engine, the stator vane having an endwall that forms a hot gas flow path through the vane, where the endwall includes a row of diffusion slots extending around both the pressure side and the suction side of the airfoil to provide film cooling. Each diffusion duct is connected to a plurality of film diffusion channels that are slanted with respect to the endwall surface. Each of the film diffusion channels is connected to a metering and impingement hole to supply cooling air to the slots. Cooling air is metered through the metering holes, then impinged against the diffusion channel and then diffused into the ducts and discharged as film cooling air over the endwall surface. The row of diffusion ducts extends along both sides of the airfoil and around the leading edge region to provide film cooling along the entire endwall.