This study was conducted in order to estimate the gene effects governing the inheritance of certain traits and to search the genetic structure of each group in a 9x9 diallel cross group established by crossing inbred lines in sunflower. In the research: (.1) Significant positive heterotic effects were observed for all the characteristics studied in different crosses. Based on the results, which are 2 or 3 parents were observed to be good general combiners for seed yield Per plants and eight crosses were the promising hybrids for seed yield/plant and plant height. (2) Both additive and dominance genetic variances were significant for all characters. Also, overall mean dominance effect of heterozygous loci, h". was significant for all characters. It was found that the frequencies of positive and negative alleles at these loci were not equal in the parents (i.e. HI > HU). The average degree of dominance showed overdominance for all characters studied.