This study was meant to provide genetic information about selection among maize hybrids for NUE, and to evaluate the role of combining ability of inbred lines in hybrid performance under N- limited conditions.Results showed that:1)High tolerance and high response(HH),hybrids 7-5x12-3 and 7-5x145-1. 2)High tolerance and low response(HL), hybrids 100x224 and 421-2xSC-10. 3)Low tolerance and high response(LH), hybrids 32-3x308 and 308x290-3- 2.4)Low tolerance and low response(LL), hybrids 100x158 and 100x421-2. NUE at low N was significantly correlated with yield at high N. Grain yield was positively significantly correlated with chlorophyll concentration, ear diameter, biomass yield, kernel number/plant. Most of studied traits of hybrids showed larger heritability under low N than under high N. Direct selection for grain yield at low N was likely to be more efficient than indirect selection for grain yield at high N for improving grain yields under low N. Both GCA and SCA are equally important for genetic variability in performance of mean yield over N levels, but for grain yield and NUE at high N, GCA plays a greater role than SCA.