Plant density affects growth characteristics and yield of sunflower via changes in space available for growth of each plant. As 100% of seeds planted never emerge, the question is that how far the planting distance could be reduced without considerable increase in competition, and how much the plants adjacent to an un-emerged plant may compensate the reductions in yield due to the lost plant. To answer this in sunflower, Hi Sun 36 hybrid, an experiment was conducted at The Agricultural Research Station, Isfahan University of Technology, using a split plot layout within a randomized complete block design with three replications. Row distance (60 and 75 cm) was the main plot and plant distances over the row (12, 14, 16, and 18 cm) were the sub-plots. In addition, to evaluate the compensation power of this hybrid, the conditions of no-missing, one missing and two missing plants were studied. The same row distances were the main plot and conditions of no-missing, one missing and two missing plants were the sub-plots. Under the conditions of no-missing plant, the effects of row and plant distances on all developmental stages were not significant, with the exception that days to physiological maturity was significantly lower at 12 cm planting distance. Plant height, stem diameter and dry weights of stem, leaves and head residues, head diameter and seed and biological yields were significantly increased, but harvest index decreased, as row distance increased,. Increase in row distance also increased oil percentage and yield. The effect of row distance on other traits was not significant. Stem diameter, dry weights of stem, leaves and head residues, head diameter, number of seeds per head, 1000-kernel weight, seed and biological yields and harvest index were significantly reduced and plant height increased as planting distance decreased. Also, seed oil percentage and oil yields were reduced as planting distance decreased. Under the conditions of missing plants and in all planting distances, seed yield increased as row distance increased, but this increase was only significant at 18 cm distance. In all planting distances, stem diameter and dry weights of stem, leaves and head residues, head diameter, number of seeds per head, 1000-kernel weight, and seed and biological yields were significantly increased as planting distance increased. Harvest index, only significantly increased as planting distance increased from 12 and 24 to 36 cm. Seed oil percentage and oil yields were increased as planting distance increased in all planting distances. Plant height showed different responses to missing plant conditions. Assuming 85% emergence and under conditions of good soil structure and permeability, the combination of 60 cm row distance and 14 cm between plants might be suitable for production of sunflower. But, the observed lodging, growth trait responses, and sensitivity of sunflower to soil structure and permeability,