Aim of our research was to study the genetic diversity and establish the inheritance of top branching trait in the collection of 34 sunflower lines of the Institute of Oilseed Crops of the NAAS. Experiments were carried out in 2005'2016 according to classical cultivation methods using manual castration crossings forced self-pollinating isolation and visual assessment of the first and second generation of obtained descendants. The statistical reliability of the obtained ratio was confirmed by calculating the Pearson's chi-squared test. Presence of two loci determining the inheritance of the branching trait in sunflower was established. In one locus recessive alleles are responsible for manifestation of the branching trait. In the second locus dominant alleles are responsible for the manifestation of the branching trait. In 23 lines of sunflower it was established that a recessive homozygote for one gene causes phenotypical top and full branching. In 8 lines of the collection full branching trait is due to the dominant allele of the gene. In the lines InK235 APS49 the presence of two genes was established the dominant alleles of which determine full branching trait. In the APS56 line full branching is controlled by the dominant alleles of three genes.