Abstract: The invention relates to a method and an apparatus for easily determining the composition of plastic waste that has been pressed into bales. Here, the proportion of plastic on at least one surface of a bale is determined with the aid of an NIR spectrum and, optionally, an image from a visual system. In a preferred embodiment, the proportion of plastic of a bale is determined on a plurality of sides of a bale. This increases the accuracy of the method. By way of the method according to the invention and the apparatus according to the invention, it is consequently possible to undertake a quality control of plastic waste that has been pressed into bales, which quality control is fast, reproducible and documentable.