Background: Today, the trademark is the heart of the company and the management of brand image and identity require certain attention and care. In an increasingly tough business climate where the brand today has a central and important role, it is understandable that the companies want to take maximum advantage of it. In the company the brand is a great resource with an already known identity and established values that can help new products to enter the market. To extend the brand is a popular growth strategy but it is important to do it properly in order not to fail. J Lindeberg and Peak Performance are two Swedish fashion companies which both have made brand extensions. They are working or have been working with similar product categories but the brands have a different image. Purpose: The purpose of this report is to investigate, describe and analyze how J Lindeberg and Peak Performance have elaborated their brand extensions. Brand extension within the fashion business is a subject that hasn’t been explored to a wide extent and that is why it feels interesting to find out more about it. Why some brands succeed and others don’t, and the key factors for a successful brand extension within the fashion business. Methodology: The thesis is a qualitative study using an abduction methodology where empirical findings and frame of reference have been studied parallell. The theoretical framework is based upon the importance of the brand and it’s structure. It also focuses on strategy for brand extension and belonging benefits and disadvantages. The empirical findings are based on interviews with employees from J Lindeberg and Peak Performance. Conclusion: It is noted that both brands have extended their brands with varied results. Both J Lindeberg and Peak Performance seem to have learned of their mistakes and today they are managing their brand more carefully. Credibility and recognition of the brand are important when extending, to help the new products when being introduced at the marketplace. The report has also revealed that brands based on image and personality, like J Lindeberg and Peak Performance, have better chance to extend, since image brands doesn’t have such a narrow focus.