Sunflower is a plant species with a prominent period of seed dormancy. Physiological maturation period can be accelerated under laboratory conditions using methods for breaking seed dormancy such as: previous cooling at 5-10°C previous heating at 30-35°C gibberellic acid treatment KNO 3 ethrel etc . The aim of this study was to determine the duration of seed dormancy period of different sunflower hybrids and parent lines produced in Serbia and to determine which of the methods for breaking seed dormancy gives the best results. Studies were carried out on five commercial sunflower hybrids and their parental components. Seed germination was determined after harvesting using standard laboratory methods and tetrazolium tests. The following methods were used for seed dormancy breaking: low temperature treatment of 5- 10°C high temperature treatment of 30-35°C and treatment with gibberellic acid. The tests were performed in the period of 30 50 and 90 days after harvesting. The application of gibberellic acid method gave the lowest values of seed germination while statistical significant differences between the control and method of low and high temperatures were not found. Sunflower hybrids Sremac Duško NS-H-111 Velja and Branko as well as the female lines of hybrid NS-H-111 and male lines of hybrids Sremac and Velja had no prominent seed dormancy 30 days after harvesting. Seed dormancy in female lines of hybrids Sremac Duško Velja and Branko and male lines of hybrids Duško NS-H-111 and Branko was decreased 90 days after storage but it was not completely removed.