The present investigation aimed to evaluate eight inbred lines of maize in diallel mating design. Twenty-eight crosses were constituted at Sedment Elgabal, Horticulture Research Station, Beni-Swef Governorate in the 2015 season, whereas parents and crosses were evaluated during 2016 season in a randomized complete block design with three replications. Results revealed highly significant variation among parents and among F1 crosses for the studied characters. Both general (GCA) and specific (SCA) combining ability variances were significant for most studied traits, revealing the important role of both additive and dominance components in the inheritance of the studied traits. The GCA/SCA ratio was less than unity for all studied characters, except for days to 50% silking, days to 50% tasseling, ear diameter and number of rows ear-1, indicating a greater contribution of non-additive than additive effects of genes in the genetic expression for these traits. The parental inbred lines P1 (INB.24), P6 (INB.72) and P7 (INB.82) were effective combiners for grain yield. The results showed that all F1's, except (INB.24 P1 x P3 INB.42) and (INB.37 P2 x P5 INB.64) reflected highly significant and positive SCA effects for grain yield. Heritability in the broad sense (h2b%) estimates was generally high for all studied traits. High heritability values coupled with high genetic advance were recorded for all studied traits, except days to 50 % silking and tasseling, and 100 kernels weight, indicating that selection would be effective in early generations.