Safflower ( Carthamustinctorius L .) is one of the first plants grown in near East, India, China and Japan. It may have been domesticated in northeastern India and in the Middle East. The plant has long been grown in Iran's agriculture as subsidiary crop and with aim of providing color from its flowers. The presence of unsaturated and essential fatty acid of linoleic in the oil, the high nutritional quality of the oil which in some instances is comparable with olive oil, plus considerable medicinal properties and extremely high compatibility of plant for growth in the dry and semi-dry lands of Iran makes the growing of safflower particularly importance. A main objective of breeding safflower is producing and introducing varieties with high yield performance. According to various reports, seed yield in safflower is genetically and environmentally influenced by the number of heads, the number of seeds in the head, thehead diameter and 100-seed weight.This experiment was conducted during 2012-2013 with the purpose of investigating the genetics of head diameter as a part of safflower yield components and the correlation between head diameter and the content of petal pigments in safflower. To achieve this goal, two genotypes obtained from USA Gene bank with substantial differences in head diameter were selected as the parental genotype of the study. One of the parents, PI 53, was a dwarf genotype, early in flowering with very small head diameter(average=19.6 mm) and had yellow petals. The other genotype, PIGL, was tall and spiny with very large diameter (average = 38 mm ) and had red petals. Direct and reciprocal crosses were made between the two genotypes and then F 2 seeds were produced by self-pollinating F1 hybrid plants. The F2 seeds were planted and the head diameter and the other yield components were measured on each plant grown. The results of analysis of variance showed that plant height, head diameter, the number of secondary shoots per plant and the number of seeds per head had a high heritability. The broad sense heritability of these traits were estimated to be 92.0, 91.0, 88.0 and 73.3% respectively. The correlation results revealed that increase in the head diameter may result in an increase in the amount of pigments present in petals and the number of seeds in the head.The results also showed that red color of petals is dominant over yellow color. Using genotypic variances of F2 offsprings and parents, it was found that probably one pair of genes is controlling the head diameter. If confirmed in future experiments these genes could be used in breeding programs of safflower.