Abstract. The objective of the study was to evaluate the impact of genetically modified (GM) ingredients (soya bean meal and maize grain) used in poultry diets on birds' performance, as well as the accumulation of the transgenic DNA in eggs, breast muscle and internal organs. In the present experiment four generations of Japanese quails, which were subject to three different diets, two containing genetically modified organisms (GMO, soya and maize) and one GMO-free control, were analysed. Birds' performance traits were monitored along the trial. A screening molecular method – polymerase chain reaction amplification (PCR) – was used to detect CaMV 35S promoter and nos terminator in the collected samples. Results showed no presence of modified DNA in the analysed products. According to the obtained results, it was concluded that there was no negative effect of the use of genetically modified soya bean meal or maize grain found with regard to final product safety for consumers or to birds' productivity.