There are few attempts at empirically validating the effectiveness of brand differentiation, leading to a long-lived debate regarding whether it is a necessary condition for brand success. Drawing from metacognition and decision process theory, the current research suggests that the relationship between perceived differentiation and purchase is stronger when there is a weaker match between the brand’s perceived position and consumers’ purchase goal (i.e. between what the brand stands for and what consumers are seeking). In addition to the condition of purchase goal, consumers’ confidence in their judgement of the brand’s position acts as an additional contingency factor in the relationship between differentiation and purchase. The hypotheses were supported by two studies across common consumer purchase goals: ‘value for money’ and ‘top of the range’ and two product categories, with different adult samples (n1 = 291 and n2 = 283 for the respective studies). Implications for brand communication strategy are discussed.