Nanocomposites of polymethylmethacrylate (PMMA) and CdSe were fabricated by a casting technique. The result showed that CdSe@PMMA can be used in white and green light emitting devices. 0.01CdSe@PMMA exhibits monochromatic green color emission with the highest fluorescent quantum yield and lowest optical band gap value, while CdSe@PMMA with other ratios shows a multicolor emission. The band-edge emits in the vicinity of 280-296 nm but a more stable intensive green color emission at 553 nm is found for 0.01CdSe@PMMA. The change in E-g (4.18 to 4.4) eV values is due to the interaction between the PMMA polymer and CdSe.