To gain a greater degree of independence from suppliers, strengthens the retail brand, have a greater market share etc., private labels are becoming increasingly important for retailers. In this respect, the transfer of a well known brand name to a new product in the same or in a different product category, known as brand or line extension, offers an opportunity to foster the achievement of the mentioned targets of retailers. In general, line and brand extensions have become a common strategy for many companies due to cost and time savings:Meanwhile, a large number of companies use these strategies for product launches. However, there are also disadvantages, for instance the parent brand can be diluted, and thus a brands reputation can be damaged. Given these potential risks, it is important for managers to be aware of potential success factors of line and brand extensions. Against the background that past research has focused on the success drivers of line and brand extensions of national brands, this thesis addresses success factors of line and brand extensions of private labels. It is also worth noting that value-added-brands and premium private labels have rarely been analysed. Therefore, the aim of the empirical analysis of this paper is to investigate the success factors of these kinds of private labels. The results, e.g., revealed that there is a significant relationship between the perceived brand-level or product-level fit and the private label extension success.