We have obtained eight degradable/biodegradable materials based on starch (certified compostable), sample 4–7, HDPE mixed with totally degradable plastic additive (TDPA), sample 2 and polyethylene with the addition of pro-oxidant additive (d2w), sample 1. Composition of sample 3 has not been reported. The materials have been tested as to the rate and character of their degradability/biodegradability in controlled composting conditions. Experiment explored also the effect of degradation/biodegradation of plastic bags on compost quality. The material of the original samples was subjected to assessment using the Nicolet 6700 FT-IR spectrometer, the outcome thereof was obtaining infrared spectra of the samples. For further specification the original samples were tested using the thermogravimetrical analysis. The texture of the foils at different stages of degradation is presented in the Scanning Electron Microscope (SEM) photographs. Plastic bags certified as compostable have degraded in laboratory conditions and their degradation had no impact on the quality and features of compost. Selected samples (4, 6) showed significant erosion on surface when subjected to the SEM analysis. Samples labeled (by their producers) as 100% degradable (samples 1, 2, 3) did not show any visual signs of degradation and the process of degradation had no impact on the quality and features of compost. Only one of the samples (sample 1) showed certain erosion of surface when submitted for the SEM analysis.