The invention describes a cushion for shading system of the type comprising a piece of cloth slidingly fastened to a section bar of an upright. A raceway with a substantially C-shaped cross section serves to fasten the cushion to a section bar edge, and a flexible tongue, having an end on the raceway and an opposed end spaced therefrom in order to contact the upright, serves as a spring between the section bar and the upright, allowing the section bar to come nearer to the upright in a compression phase or to be spaced in a predetermined way in the absence of compression.