This research aimed to evaluate the general and specific combining ability components for six inbred lines and 15 hybrids produced by a half diallel cross method, and was conducted during 2010-2011 seasons, in the Department of the Maize Researches at G.C.S.A.R. Damascus . The evaluation included the grain yield, ear height, ear length, and silking under two different treatments of nitrogen fertilizer (1- addition of 50% of N-fertilizer with sowing and the other 50% one month after sowing. 2- addition of 50% of N-fertilizer 18 days after sowing and 50% one month after sowing).and 3 replicates. Results indicated that: Mean squares of inbred lines, and hybrids were highly significant for all studied traits under two adding dates of nitrogen fertilizer, which indicated the presence of genetic distance among parental lines. The ratios (
2 GCA/
2 SCA) showed that additive gene effect was more important than non-additive gene effect in controlling all studied traits except grain yield which showed dominance of non-additive gene effect under tow dates. Many of significant positive GCA effects were obtained for all traits, therefore, it could be concluded, that the inbred lines CML.330, IL.26-09 and CML.334 seemed to be the best general combiners for grain yield. The hybrid (CML.368 × IL.215-09) had showed the best specific combining ability effects for grain yield under the first date, while the hybrid (CML.330 × IL.26-09) showed the best SCA effects under the second date. The second adding date of nitrogen fertilizer (50% 18 days after sowing and 50% one month after sowing) had surpassed of the first date (50% with sowing and 50% one month after) with significant effects for grain yield trait.