Abstract: A half diallel set of crosses among six inbred lines of maize were evaluated under two plant densities (normal and stress densities) to study phenotypic and genotypic correlation coefficients, hertability and expected gains from direct and indirect for some flowering and vegetative and yield and yield components traits. Obtained results show: Expected gains in grain yield from indirect selection for flowering and vegetative traits under both plant densities and their percents to gain from direct selection were high values for Ear height and plant height and moderate values for ear leaf area. Expected gains in grain yield from indirect selection for yield and yield components under both plant densities and their percents to gain from direct selection were high values for Kernels number per row, 100 kernel weight and shelling percentage. Expected gains in grain yield from indirect selection for quality traits under both plant densities and their percents to gain from direct selection were high values for oil percentage. Grain yield plant-1 was positively and significantly correlated with stem diameter at normal plant density. Grain yield plant-1 was positively and significantly correlated with kernels No. row-1 at both plant densities. Genetic and environmental variances for flowering and vegetative traits at stress plant density were higher than that at normal plant density for plant height and ear height. Genetic and environmental variances for yield and yield component at stress plant density was higher than that at normal plant density for kernels number per row. Broad-sense heritability estimates was 99.9 for kernels No. row-1, 100 kernels weight, shelling percentage, carotene percentage and 99.6 for plant height at both plant densities.