This research tests the plastic materials which can provide properly diffused illumination level and have smooth transmittance performance. Among these materials, two of them, PVC (polyvinylchloride) and PMMA (polymethylmethacrylate) sheets are evaluated, compared with each other and application possibilities. Besides, one of most important evaluation criteria for efficient lighting in office spaces; transmission property of these materials is empirically tested in laboratory in the scope of this study. One of these, PMMA is produced on commercial purpose in Turkey and used with its well known name; Plexiglas and the other one; Barrisol is an officially registered trademark of PVC translucent strech sample used in test. This study is gathered by means of searching lighting literature, rather restricting the data about two specific plastic based materials used in offices and experimenting the transmission characteristics of plexiglas and Barrisol. Scientifically; transmitting and diffusing of a material are unattached properties and rather concerned with chemistry. But there is a measured certainity that Plexiglas has %92 and Barrisol %73 percentage of transmission value. The results of test also supports that; transmission percentage of plexiglas sample is higher than Barrisol. It is reached to the conclusion that; when light directly comes down on a workplane whithout being regularly dispersed, it will tire viewer.s eyes and deteriorate visual comfort, negatively affecting productivity in offices.