Abstract: LC-MS/MS was applied to the determination of 8 fluorescent whitenings i.e., FWA135, FWA184, FWA185, FWA199, FWA367, FWA368, FWA378 and FWA393 in foamed plastic tablewares. The sample was extracted with trichloromethane, and the polymers in the extracts were precipirated by methanol. Analytes in the filtered extract were separated by LC, using Eclipse Plus C₁₈ chromatographic column as stationary phase, and mixtures of 0.1% (φ) formic acid-H₂O solution and 0.1% (the φ) formic acid-methanol solution mixed in various ratios as mobile phase in gradient elution. ESI⁺ and multi-reactions monitoring were adopted in MS/MS. Linearity ranges of the 8 fluorescent whitenings were found in the same range of 1.00-250 μg·L^-1 with detection limits (3S/N) in the range of 0.5-2.0 μg·L^-1. On the base of blank sample, test for recovery was made by standard addition method; values of recovery found were in the range of 85.2%-98.4%, with RSD's (n=6) in the range of 4.1%-8.3%.