The significance of the internet as a distribution and sales channel has rapidly increased in recent times. Search engines play a crucial regulatory role in this context. This has led to the development of a specific advertising strategy for search engines known as keyword advertising. However, the legal permissibility of keyword advertising in terms of trademark and unfair competition law, as well as the relationship between trademark and unfair competition law, remains controversial. Thomas Kaps first analyzes the central trademark law element of trademark use and presents the development of the case law of the European Court of Justice (ECJ). Building on this, he examines potential trademark infringements caused by keyword advertising, distinguishing between visible and invisible keyword advertising. He also highlights the diverging case law of German and Austrian supreme courts.