Every branch of law is based on certain constructions with a high degree of generalization and abstraction called fundamental principles, which express in a concentrated form the objectives which are then developed by particular legal norms that regulate social relations.

The principle of reciprocity and the principle of non-discrimination have general application and are indispensable. Their coexistence and interdependence is manifested and plays an important role in the development of inter-state relations governed by the rules of diplomatic law, being designed to guide international relations between states and having a special significance for the cooperation between the topics of the international community, for the preservation of international peace and security. We will analyze in this paper the application of these two principles in matters such as the establishment of the class and rank of diplomatic missions and the granting of diplomatic immunities and privileges. For the elaboration of the paper we have used as research methods the analysis of the problems generated by the mentioned subject with regard to the doctrinal views expressed in the treaties and papers, the documentary research, the interpretation of legal norms in the matter.