To measure the orientational state of opaque high-impact polystyrene (HIPS) samples, the dichroic ratios of different absorption bands have been determined in the near-infrared (NIR) transmission spectra measured with polarized radiation. For injection molded plates, dichroic ratios close to one were observed, indicating very low orientation effects in these specimens. However, a larger anisotropy was detected in the thermoformed cups and additionally different processing conditions could be discriminated by the dichroic effects in the NIR polarization spectra. Thus, NIR transmission spectroscopy with polarized radiation proved to be a convenient and rapid tool to determine orientation phenomena in HIPS samples and may also be implemented as a light-fiber-coupled on-line process control technique.