Abstract: A light diffuser attachment particularly adapted for use with a self contained fluorescent lamp fixture of the type having a fixture body cover which includes the fluorescent tube and operative components therein and a diffuser receiving flange or rim thereon. The diffuser attachment has a generally box-like configuration and is fabricated from conventional plastic diffuser material so as to have a bottom wall, side walls, end walls and an open top end. Locating and mounting beads are disposed generally longitudinally along the inside of the diffuser side walls adjacent the open end. Selected of the beads on each side wall are laterally spaced apart from each other to define a flange or rim receiving channel therebetween which receives the diffuser receiving flange or rim of the fixture body cover therein.