[EN] To evaluate the quality of service it is critical to know the concepts on which such evaluations are made from the user point of view. Differential semantics was applied in an emotional design framework to identify these concepts, or dimensions, and an equation was devised to discover the influence they have in the acceptance of a service by users. Some 53 users evaluated the tangible elements of 28 library information desks. Five latent concepts emerged from the analysis: modern, welcoming, professional, simple, and accessible. The most influential concepts influencing willingness to interact at library information desks were, in descending order, modernity, professionalism, welcoming environment, and accessibility. Finally, a comparative semantic profile was developed to explore the perception differences between the most and the least desirable information desks. Understanding the concepts that users consider when evaluating information desks and the influence of those concepts on user behavior can help designers improve overall service quality impressions.