Six population seeds of three yellow maize hybrids were formed at Agricultural Research Center, Homs, during 2008 and 2009 growing seasons. Their plants were evaluated in 2010. The present work aims to determine the genetic parameters in six populations (P1, P2, F1, F2, BC1, and BC2). Mean square results showed significant differences among mean values for all traits in all crosses. Significant heterosis values were positive and relative comparing to mid and better parent for most traits. The potence ratios exceeded (+1) in all traits and crosses except ear height, indicating thus over-dominance. In breeding, depression values were significant in most traits for Cross-1, while their values were non- significant in all traits for Cross-2 except plant height, and also in Cross-3 except plant height and grain yield per plant. In most traits epestasis or dominance gene action occupied the first rank in the genetic effects in order of importance to cross, with the exception of number of rows per ear, number of kernels per row and grain yield per plant where additive gene action occupied the first rank for Cross-2 and Cross-1 respectively. Therefore, it could be suggested that selection for most studied traits in the subsequent generations will be relatively more effective than in the early generations.