Cities and their infrastructure have become extremely complex systems that face numerous challenges in terms of effectively responding to the daily needs of their citizens. Considering the fact that today most cities in the world are affected by an accelerated process of urbanization, which results in an increase in the consumption of food, water and energy, there is a need for efficient city infrastructure and mobility, i.e. the need for the introduction of smart technologies that will optimize their consumption, and which will result in a reduction in citizens' living expenses. A smart city uses information and communication technologies with the basic goal of exchanging information with the public and improving the quality of services, that is, overall, to increase operational efficiency, all for the benefit of citizens. In order to better understand the subject of a smart city, the term smart city will be defined in the final paper, the time sequence of their development will be presented, will be analyzed the information and communication technologies which use in their implementation and their effect on sustainable development. Also, the paper will present an analysis of the smart cities Shanghai and Rijeka, i.e. all the technological innovations applied by these cities, which present them as smart, will be analyzed.