Abstract: A multipurpose valance assembly is provided in which valance attachments may be removeably engaged to a valance base or a preexisting window treatment system. Each valance attachment holds a decorative insert, which may be a conventional valance or a drapery fabric panel assembly. Because the invention allows for multiple valance attachments in adjustable engagement with one another, and a variety of interchangeable decorative inserts, the multipurpose valance assembly creates a wide array of new decorative effects. In addition, a valance adapter allows the invention to be retrofit to preexisting window treatment systems, substantially reducing the labor and material costs associated with installing new window treatment systems.