For some time past, the main focus in urban development concentrates on a new approach. Thereby, this concept of the Smart City should face several urban challenges triggered by rapid population growth and environmental changes such as climate change and high consumption of resources. Currently, cities of different size and with various, individual challenges are seeking to rank among the world's leading smart cities. At the same time, a lively debate regarding definitions, roles and critical trends is still consisting within the scientific discourse. Thus, there are numerous possibilities of developing cities smartly. Due to the increasing popularity of the concept, initial assessments and reports regarding the comparison of smartness of several cities rapidly emerged. Especially Vienna used its first place in the international Smart City Ranking of Boyd Cohen in 2011 to create a strong image of a so-called Smart City. Thereby, the instrument of rankings constitutes a commonly used method to effectively communicate comparisons of cities, regions or countries in public. This important role as positioning instrument predominantly relates to the increasing competition between cities, resulting from globalization processes. But what is a Smart City and which cities can actually be considered as smart? Furthermore, the concept of Smart Cities contains numerous topic areas, which is the reason why it is often characterized as a generic approach. This leads to the situation that many cities are defining the concept of the Smart City corresponding to their own challenges and priorities. In this context the question remains, if rankings are able to represent the positions of the compared smart cities reasonable. Within this master thesis, these and other questions will be investigated. Altogether, the definition of the term smart and the concept of the Smart City are still unclear. Furthermore, these problems come into conflict with the methodological diversity and other problems of comparative urban analysis. For that reason, the concept of the Smart City and already published Smart City Rankings will be critically analyzed.