The study determined that polarized light is useful for the forensic comparisons of passport films by measuring FT-IR spectra. The peak ratio analysis could not distinguish the passport samples when nonpolarized light was used; however, when polarized light was used, the passport samples were successfully distinguished by comparing the peak ratios. Films that are used on the biographical data page of forged passports usually differ from those of genuine passports because it is difficult to obtain genuine films; therefore, a detailed examination of the characteristics of the film can be effective in passport examination. In the current study, both genuine and counterfeit Japanese passports were examined by analyzing the films on the biographical data page. Thirty genuine and 35 counterfeit passports and five marketed films pasted on name cards were examined. The absorption spectra were obtained by the Kramers-Kronig transformations of reflectance spectra. The peak ratios were then calculated from the absorption spectra by adding the peak areas at 1,126 and 1,263 cm to the power of minus one and dividing the result by the peak areas at 1,717 cm to the power of minus 1. 1 table, 6 figures, and 4 references