This work focuses on the cogasification of lignite and fresh polyethylene (PE) granulate at lignite ratios ranging from: 0 to 100% in the dual fluidized bed pilot plant at Vienna University of Technology. The operating parameters for all gasification and cogasification tests were kept constant. The input fuel power was 90 kW(th), while the gasification temperature was 850 degrees C. Olivine was used as the bed material. In addition to standard online measurements of the permanent components of the product gas, the tar content was also measured. Using lignite in the feedstock improved quality in terms of reducing tar load and increasing the possibility of adjusting the main components of the product gas. The beneficial effects of lignite could even be attained at low concentrations of lignite in the fuel mix with PE.