The study addresses the issue of contractual and non-contractual third-party liability. It primarily focuses on the long-discussed question of the basis and conditions under which liability according to contractual principles is possible when the liable party is not contractually bound to the injured party. This question has gained new relevance in light of the Law for the Modernization of Obligation Law of November 26, 2001. With Sections 280 (1), 241 (2), and 311 (3) of the German Civil Code (BGB), the law now provides a legal basis that can be used to address the issue of third-party liability. However, the statutory regulation leaves several questions unanswered, which this study aims to explore. The primary goal is to appropriately resolve the problems associated with contractual third-party liability based on Sections 280 (1), 241 (2), and 311 (3) of the BGB and to establish a secure doctrinal foundation for the liability conditions.