This master thesis deals with the two currently widely debated design styles in user interface design: Skeuomorphism and Flat Design. Skeuomorphism describes the imitation of characteristics of a real-world object (which had been used especially by Apple on the iPhone before iOS 7). Flat Design on the other hand uses a simple, two-dimensional, “digital-authentic” style (which had been used by Microsoft on Windows Phone and the operating system Windows 8). Both design styles are often used in comparison with each other. This thesis wants to find out if one design style will dominate over the other in the future, if designers have to decide between the two or if the solution to the discussion is a compromise.