The sorption behavior of a fluorescent reagent into a polymer film was visualized by confocal laser scanning microscope (CLSM), and the effect of additives on the sorption was examined. Perylene and cellulose acetate (CA) were used as a fluorescent reagent and a polymer material, respectively. Perylene dissolved in additives of glycerol triacetate (GTA), triethylene glycol diacetate (TEGDA), 1,3-butylene glycol diacetate (BGDA), paraffin liquid, and poly(ethylene glycol) 200 (PEG) were added onto CA film. At optimized CLSM conditions (scanning range of a 10 mu m-depth from the CA film surface with 1 mu m intervals and a scanning speed of 1 fps), the sorption of perylene at the inner CA film was determined. Diffusion coefficients of perylene in the CA film were calculated according to Fick's second law. When perylene was dissolved in TEGDA, the highest diffusion coefficient, 8.9 x 10(-15) m(2)/s, among the additives was obtained because of high affinity of TEGDA with perylene, whereas the lowest diffusion coefficient was observed in paraffin liquid, which showed a low affinity with perylene. The diffusion coefficients of perylene in GTA, BGDA, and PEG also revealed that physical parameters, such as molecular size and viscosity, of the additives were additional factors affecting the perylene diffusivity in the CA film. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1710-1717,2010