The Preliminary ruling procedure institute is established by the Threaty, regulated by the article 267 of the Threaty of Functioning of the European Union, which allows access of nacional courts to the European court. The purpose of the Preliminary ruling procedure is to ensure uniformity in application of European Law in all Member States. Although any Nacional Court has jurisdiction to refer the matter during any proceedings, European Court has the final word in the defining the concept of a court of tribunal, he is deciding wheater the court is in the meaning od the article 267. The purpose of this paper is to analize the part of National Court in preliminary procedure considering that they are initiators of procedure itself. The preliminary procedure is initiated for the purposes of the interpretation of the Threaty and the validaty or interpretation of acts adopted by the institutions and bodies of the European Union. Furthermore, it is important to clarify in which situation the national court enjoys discretion, when they are obliged to refer the question, or in which they are bound to do so. It is analyzed in short lines in which stage and in which form preliminary question should be asked. If national court fail to refer the question, and they had an obligation to do so, there may be some consequences, which is to be completed in the end of this work.