The method for modifying the content of a target area in a television image comprises generating an original image signal (PGM1) by means of a camera, processing the original image signal by adding graphics into the television image, determining the target area in the television image, transmitting further the processed image signal (PGM2) and the target area determining data, and inserting, at a later stage of the signal transmission chain, substitutive content to the target area according to the target area determining data. According to the present invention, the graphics is added into the television image according to a predetermined graphics percentage of coverage; and to the shared area of the target area and the additional graphics area, the substitutive content is inserted according to the residual percentage of coverage not covered by the added graphics.