A field experiment was conducted at the Production and Experiment Station in Bałcyny in north-eastern Poland (53^o35’ N; 19^o51’ E) during the years 2003-2005 to evaluate the effect of different levels of nitrogen fertilization on the yield and qualitative characters of two hybrid grain maize cultivars, Junak (FAO 210-220) and Boruta (FAO 230-240). The morphological characters of maize plants, grain yield and yield structure were determined, and grain samples were subjected to chemical analyses. It was found that the grain yield of maize grown in north-eastern Poland ranged from 6.67 to 11.16 t·ha^-1, and it was greatly dependent on temperature and moisture conditions in particular years of the study. Cv. Junak was characterized by a higher yield in the wet year, while cv. Boruta showed a higher yield in years with more favorable weather conditions. A high and comparable grain yield (8.48 and 8.68 t·ha^-1) was reported for both cultivars, despite differences between them in respect of the maturity class (FAO ripeness class). This indicates that the grain maize cultivars Junak and Boruta are suitable for growing in north-eastern Poland. Nitrogen applied at rates of up to 150 kg N·ha^-1 contributed to a steady increase in grain yield. Nitrogen fertilization at a level of 150 kg N·ha^-1 was sufficient for cv. Junak, whereas in cv. Boruta the rate of nitrogen could be increased to 180 kg N·ha^-1.

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