Neutralization of the amount of plastic packaging waste from year to year is becoming an increasingly serious problem. Replacing some of them with the products made of biodegradable and oxo-biodegradable polymers, which may be broken down in the environment in a shorter time seems to be one solution. Polymers are used both for the production of bags for biodegradable waste, as well as shopping bags, labeled by the producers as “compostable”, “biodegradable”, etc. Therefore, they are often used to collect bio-waste, with which they go to the installations intended for their processing, e.g. composting plant. However, contrary to the information on the package, not all are decomposed under the conditions prevailing in composting plants. The aim of this study was to assess the degree of decomposition of selected package from biodegradable and oxo-biodegradable polymers under the actual conditions of an industrial composting plants and the possibility of contamination of the product (compost) with components originating from, among others from the additives that improve the properties of plastics and dyes. The conducted research has shown that many bags and sacks available in retail chains, contrary to the information provided, are not completely degraded in industrial composting plants, and may also become a source of heavy metal pollution.