Additives distributed in a polymer film were visualized by a confocal laser scanning microscope (CLSM) in this study. Cellulose acetate (CA) was used as the polymer film material. Perylene as a fluorescence reagent and glycerol triacetate (GTA) as a plasticizer for CA, respectively, were selected and mixed for visualizing the absorption of perylene into CA. Under optimized CLSM conditions of an objective lens (dry, 20x) and diode laser (408 nm, 290-330 mu W), a fluorescent penetrant, perylene, in GTA solution was detected in CA casting film within around 9 pin depth of the film in 60 minutes after starting the sorption study. It was also found that the fluorescence intensity of perylene became lower with the film depth. This finding suggested that CLSM could visualize the sorption behavior of perylene as a dynamic diffusion process. Analytical conditions, such as a scanning range along the Z axis (+/- 10 or +/- 30 mu m from an air-contact surface of the CA film) and a scan speed (1 or 30 fps) of CLSM, did not affect the fluorescence intensity of the sorbed perylene. It was concluded that a newly developed analytical methodology using CLSM was sufficient for visualizing the perylene penetrant across the cross-sectional distribution of the CA film, being capable of monitoring the sorption behavior of compounds in polymer materials without any destruction of a given absorbed film. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1552-1557, 2010