In some applications of diffusers, it-is desirable to minimize the diffuse back reflection of light. Use of polarized light is one way to reduce this back reflection. To that end, the effect of diffusers on polarized light is studied experimentally. Diffusers based on ground glass, white plastic containing scatterers, and holographic optical elements are considered. The ground glass and holographic optical element (HOE) diffusers preserve polarization in the diffusion process, but the white plastic does not. Diffuse back reflection from ground glass or holographic diffusers can be significantly reduced using an isolator based on a quarter-wave plate.