The question of approaches to defining the content of the closest connection principle is one of the most important and neglected in private international law. The research is devoted to the conflict, material legal (mixed) and subjective approaches. Special attention is given to a mixed approach that fully exposes the content of the closest connection and, therefore, receiving more development in the law of the United States, the EU, China, Russia and other countries. It is concluded that the mechanism of the mixed approach is based on simultaneous account of the public interests and conflicting presumptions. The public interest, as a vector, together with the appropriate amount of presumption form the closest connection to the legal relationship. On the basis of a detailed analysis of the legal norms it is established that under the mixed approach the modern legislation uses several ways to consolidate public interest in order to determine the closest connection. The legislator either specifies the public interests (objectives) to the law enforcer that must be taken into account and not infringed, or sets whose interests the law enforcer must promote in choosing the law, or directly allocates specific criterion for such interests. The author analyzes the reasons for the uncertainty and inconsistency of the subjective approach based principally on a lawyer's search of presumed intentions of the parties and, therefore, is not only a synonym, but also a recurrence of the rejected by the contemporary private international law approach on hypothetical will of the parties.