This thesis explores the functioning of the Modruš estate in the second half of the 15th century, more precisely in the period between the 1449 division of the Frankapan patrimony and the Ottoman destruction of Modruš in 1493, during which the estate was under the control of the Modruš branch of the Frankapani. The thesis is divided in three chapters. The first provide overview of the history of the Frankapani of Modruš and the Modruš estate in the second half of the fifteenth century. The second chapter focuses on the Tržan castle located next to the city of Modruš as the center of the estate. The third, and in a way, the main chapter analyzes the spatial organization of the estate as well as the changing demography and economy on the basis of the 1486 urbarium of the estate. Using the references found in the urbarium as well as toponyms preserved in local memory, the thesis situates the Modruš estate, its main administrative nodes and churches and its villages, in fixed geographical border. It places its demographical and economic development, including the position of the serfs of the estate, all severely impacted by the Ottoman incursions after the 1460s, in the context of other well-studied estates from neighboring Slavonia and Hungary, whether aristocratic or monastic ones.