A drywall extension sleeve for an electrical box includes a rectangular sleeve with upper and lower flanges. The extension box preferably has an outer dimension that mates with a drywall ring or box. The sleeve is preferably attached to a pre-wired assembly which includes an electric cable and electrical box, drywall ring and the electrical component wired to the cable. The extension sleeve is positioned between the drywall ring or box and the electrical component. The electrical assembly is installed and drywall is then attached to the framed-in wall. An opening is provided through the drywall for the electrical component. The electrical component is then loosened and the extension sleeve and electrical component moved outwardly. Retention clips are placed in upper and lower flanges of the extension sleeve and the electrical component is tightened, drawing the extension and the component flush against the outer surface of the drywall.