This thesis explains the purpose of the UN agency UNESCO and introduces us with the UNESCO protection. Throughout this thesis are shown criteria necessary for the enlistment to the list of UNESCO's protected heritage. The Republic of Croatia has 10 locations that are enlisted on the list of protected heritage. The thesis focuses on the development of tourism in 3 cities that are under the protection of UNESCO. Dubrovnik has been inscribed in 1979. From that point onwards Dubrovnik excels on significant development in terms of number of visitors, number of stays and number of beds. The number of days that tourists spend in Dubrovnik are lesser, and Dubrovnik battles with too many cruise ships and visitors who spend only few hours on the old town, and the leave the city where they have been the cause of the crowd and pollution. The historical complex of Split and the Diocletian’s palace has been inscribed on the list of UNESCO's heritage protection in 1979. During 40 years, Split has successfully increased the number of tourists and the overnights and number of beds. Just like Dubrovnik, Split battles similar problems. Rapid increase of tourists in the last few years, also the increase of used beds have left their toll on the life on the city. Tourists visit Split for a brief time just like visitors from cruise ships which make crowds and disrupt normal life of citizens. Trogir is the city which was the last to be put under the protection of UNESCO. Since 1997 until now, Trogir had increased the number of tourists from five to hundred thousand. Number of overnights per person has decreased in relations to 1997 while the number of beds hasn’t grown significantly. Trogir is example of tourism development which the rest of cities should follow. It is visited just by tourists that spend few days in it, so it doesn’t have one day visits. In all cities interest for resources which those cities brought to protection of UNESCO is decreased.