The beginnings of tyranny can be found in some Greek polises in as early as 7th century BC, when individuals started to rule without the will of the ruling oligarchy. A violent usurpation of power also happened on the island of Sicily in Syracuse in 5th century BC, and one of it's most successful tyrans was Dionysius the Elder (406. – 367.), otherwise known for his collonial activities in the Adriatic. He was succeeded by his son Dionysius the Younger (367. – 357., 346. ‒ 344.). In this thesis the emphasis will be on comparison of ideologies and psychological profiles between Dionysius the Elder and Dionysius the Younger, based on different information established by some ancient sources (Plato, Diodorus Siculus, Polybius, Plutarch, Diogenes Laertius etc.) and determination of reasons for their success or failure based on the concept of tyranny developed by philosophers Plato and Aristotle in their political writings. In fact, father and son as rulers were completely different. Dionysius the Elder, through his ability, ambition and many battles which he dominated, created a great empire not just on Sicily, but also throughout Adriatic. Everything he created started to fall apart after his death, during the rule of his son, who lacked military and political leadership skills.