The national legislation must function according to the process of transposing the principles of the European Directives in the field of public procurement and not be "crowded" with detailed elements that would overshadow these principles. The purpose of the study is to elucidate the impact of the effective application of the principles in the contractual relations created between the contracting authority and the economic operator, within the public procurement procedures. In that sense, credibility is one of the main elements in creating and maintaining effective contractual relationships. During the study, both traditional research methods, complex and systemic analysis, the comparison method, logical and methodological analysis, but also other modern study methods were used. Research results: Currently, the biggest challenges are: weak and inefficient public procurement planning, low-quality drafting of technical specifications and tender documents, and insufficient monitoring of the execution of public procurement contracts. Thus, the reasoning of the national and European court is based on the feelings of trust and credibility that the parties to the public procurement contract will take into account for the smooth development of the future contract. If anti-competitive circumstances are detected, the investigated economic operator will bear the consequences expressly provided by the legislation, such as: monetary sanctions, compensation of the injured persons, etc. Therefore, obtaining an efficient and credible system of public procurement is one of the fundamental elements of the development process of Moldova.