Ever since the appearance of Aaker and Keller's (1990) seminal article, the brand extension research stream has intensively investigated factors that impact consumer evaluations of brand extensions. However, the main effect of product difficulty and the interactions between the parent brand quality and fit variables have not been consistent across studies. We conjecture that this inconclusiveness of findings is due to an equivocal conceptualization and operationalization of the key concepts - product difficulty and product difficulty incongruity. The existing studies mainly focus on product difficulty, i.e., the perceived difficulty level of designing and making the extension, whereas the latter refers to the difference between consumers' perceptions of the difficulty of designing and making the parent product and the difficulty in designing and making the extension product. We specifically propose that product difficulty incongruity will negatively impact consumer evaluation of brand extensions, and this negative effect is stronger for high parent brand quality and consumers with high levels of need for cognition. The findings from two empirical studies well support our predictions. © 2010 Elsevier Ltd.