Serbian cities and municipalities are facing many challenges when adopting spatial and urban plans and implementing them. One aspect, which is often mentioned by Serbian planners, is that the implementation of legal obligations, which are provided mainly by the 2009 Law on Planning and Construction, is insufficient. Another main aspect is that the degree of plan implementation is not very high. Both aspects lead to the hypothesis that the adoption of spatial and urban plans is done formally, especially because of the legal obligation, but the role and importance of the plans is neglected in reality, which is why plan implementation seems to be poor. The framework and preconditions of the case studies Subotica and Petrovac na Mlavi are different which is intended. Subotica is a city in the very north of the rather prosperous Autonomous Region of Vojvodina. Petrovac na Mlavi on the other hand is a municipality close to the Romanian border in the east of Serbia and is strongly influenced by agricultural structures. It can be concluded that smaller municipalities like Petrovac seem to have more problems with adopting and implementing plans, especially in regard to capacities of planning staff. The local level, i.e. cities and municipalities, is overstrained with the provided planning system. The 2009 Law on Planning and Construction requires the adoption of many different spatial and urban plans (municipal spatial plans, arrangement schemes, general urban plans, general regulation plans, detailed regulation plans, urban projects). The capacities of Serbian cities and municipalities are absolutely not sufficient to do this in an appropriate way. That is why they are already overstrained to adopt this large number of different plans. Adopting these plans takes a very long time. Because of that, there are absolutely no capacities to have the implementation of these plans in mind. In order to achieve a higher degree of plan implementation, reshaping and simplification of the planning system on the local level, with regard to the provided planning instruments, has to be forced. With a clearer structure of local planning instruments, plan implementation could reach a higher degree. Also the question, whether plans are realistic, has to be considered. The analysis of planning documents in the two case studies hypothesizes that the provided planning ideas, measures and goals are too ambitious. One main step towards a higher degree of plan implementation is to create realistic and realizable plans.