The contract with protective effect in favor of third parties is a long-recognized institution of German private law. Nevertheless, this legal figure is still far from being uniformly applied even after the modernization of the law of obligations, with the greatest difficulty being determining the circle of third parties to be included in the protective scope of the contract. This is particularly due to the fact that the legal basis of the contract with protective effect in favor of third parties, and consequently its factual prerequisites and scope of application, remain unclear. This study contributes to clarifying the outlined problems. The main focus is on the practically significant third-party liability of so-called experts. The investigation shows that such third-party liability cannot be justified using this legal institution in contradiction to the case law.