Card sorting is a method for eliciting mental models and is frequently used for creating efficient website navigation structures. The present studies set out to validate card sorting by linking browsing performance to the degree of match between the mental model and the navigation structure. First, a card sorting study was conducted (n = 27) to elicit users' mental model of municipal websites. Second, performance was measured for a number of search tasks with varying degrees of congruence with users' mental model (n = 50). Analysis by linear mixed-effect models suggests that the match between mental model and website structure has no effect on browsing performance. We discuss possible reasons and consequences of the failure to validate card sorting for designing navigation structures of informational websites. ARTICLE HISTORY