Cornices work basically the same way as a valance, providing a decorative top treatment to a window, hiding traverse rods or the tops of stationary side panels.  But cornices possess a couple of features that make them unique from valances. First of all, a cornice is not free-hanging design off a pole or board.  It is constructed out of a solid board, either straight at the top & bottom or shaped on either edge – the possibilities are endless.   Cornice patterns include repeating patterns such as arches or scallops or more symmetrical designs.

The​ cornice board is padded and the fabric is stretched tight over the board, in most cases resulting in a smooth surface.  (Exceptions are cornices made with folded fabric.) Welt or gimp trim finishes off the edge of the cornice.

​Cornices are great light-blockers.  Because the board returns to the walls on both the sides and the top of the cornice, they are ideal for pairing with room-darkening drapery panels in media rooms and master bedrooms for the ultimate light-blocking coverage.  Extend the sides of thecornice down the length of the window and you have a lambrequin or cantonniere style.  This style works well with a blackout cellular or roller shade for blocking light leakage. 

​This cornice has enough room behind it for a roman shade.  Cornices work well for hiding cellular shades.