Changes in substantive legislation always bring some procedural dilemmas into the work of the administrative units. The master thesis thoroughly analyses the new material legislation in the field of building construction, in comparison with the previous one and in comparison with the provisions of the procedural law. In preparing my master's thesis, I applied the method of researching and analysing existing literature, which provided me with the necessary material for a detailed examination of the research topic. With the help of the description method, I researched the legality of the operation of the administrative bodies and the main procedural institutes. Using a historical and comparative method, I analysed what changes the new legislation brings about in comparison with the previous one. With the help of the survey method in the form of a questionnaire I collected and analysed data among the officials at administrative units, and with the help of the method of deduction and evaluation of acquired theoretical knowledge, I gave my own conclusions on the subject. In my master's thesis, I examined whether the new construction legislation was adopted mainly due to the guidelines of the European Commission. The hypothesis was confirmed. Through research in administrative units, I determined whether the new law would bring procedural simplifications for all parties involved, i.e. investors, designers, side participants as administrative consultants, and whether the new institute of preliminary decision as a guarantee act in the construction process would increase the legal security of the investors. On the basis of the analysis and the research conducted, I have rejected both hypotheses. The research results of the master's thesis can serve as an instrument for further expansion of the research. The contribution of the master's thesis to administrative law and the administrative profession is reflected in the comprehensive theoretical treatment of the new legislation as well as in the comparative analysis of individual provisions with regard to the previous regulation and with the procedural provisions to the procedural rules.