The article contains an overview of the rules relating to the scope of application of the EU private international law regulations. It addresses the treatment of the relevant preliminary questions, with special reference to the Succession Regulation. The issues are discussed in three steps. The first is connected with the way of interpreting the notions and concepts, such as marriage, adoption, legal capacity etc., where such matters as personal status, legal capacity or family relationship may come to the foreground as a preliminary question. The second is dealing with the law applicable to the preliminary question. The author compares pros and cons of the “independent reference” (lex fori) and the “dependent reference” (lex causae) solutions, considering the latter as less effective, producing more negative consequences. The third step embraces questions relating to the jurisdiction with respect to preliminary question.