An adjustable shelving assembly and a support structure for supporting the adjustable shelf assembly. The adjustable shelf assembly may include at least one extension shelf unit, slidably oriented with respect to a central shelf unit such that the width and/or depth of the shelf may be adjusted. The adjustable shelf assembly may be adjusted without removing the shelf from the accompanying support structure or causing the central shelf unit to be moved. The adjustable shelf assembly may also include structure for receiving advertisements, product identifiers or the like.