The paper first explores certain aspects of dispute resolution mechanism implemented within the World Trade Organization and then proceeds with the legal analysis of a number of legal presumptions, concepts and principles both of procedural and substantive legal nature developed and applicable within the framework of the above mentioned mechanism for resolving disputes between the WTO member-states. The Paper examines the main features that distinguish the dispute resolution mechanism used within the WTO from the GATT mechanism, which mechanism, i/e/ the one implemented within the WTO framework, is recognized to be more legal in nature in contrast to the more political nature of the GATT dispute resolution mechanism, given that under the GATT mechanism the direct negotiations had more weight in reaching the final settlement than within the WTO system, where formal juridical disciplines, as the practice of dispute settlement indicates, play far more role and has become a key element of the system. Also, certain procedural presumptions and principles applicable in the adjudication process as well as the procedure and feature characteristic for the enforcement of decisions are examined in the paper based on and with reference to the number of panel and Appellate Body decisions. Decisions delivered by panels and the Appelate Body represent a very important tool for the interpretation of the WTO law and shapes the practice of its implementation. In this regard, although it is not considered a formal source, Appelate Body and panel decisions should be considered as an important source of both procedural and substantive WTO law. The DSB practice established under the GATT/WTO law, on the one hand, defines a set of applicable procedural rules and on the other hand, develops the WTO substantive law by way of developing the criteria and rules governing the application of provisions of the WTO agreements and other sources governing rights and obligations of the member-states. Particular attention in this regard is paid to the peculiarities of the application of the principle of responsibility for lawful actions applied in the WTO jurisprudence, under the relevant WTO agreements and more specifically under the GATT, GATS, TRIPS and SCM Agreements. Also a number of procedural concepts the principles e.g. the “prima facie case”, “rational relationship” elaborated in the “Hormone” case, principle of multi-criteria assessment initially applied in «Korea - fresh, chilled and frozen meat» case and negative presumption rule applied by the panels are analysied.