OBJECTIVES: Despite the increased use of generic medicines, little is known about patients' attitudes towards them and patients' decision-making process of the medicine purchased.  The aim of the study is to assess the patients’ preference structure for generic and branded over-the-counter (OTC) pain medicines and their price elasticity. METHODS: Finnish university students (n=209) responded to an adaptive conjoint analysis (ACA) interview. Product attributes of price, brand, onset time of effect, place of purchase and source of information were included on the basis of the literature, a focus group and a pilot study. The descriptors of the respondents included socioeconomic background, involvement with the purchase process, and health behavior. Individual-level utility functions were estimated, preference clusters identified, and price elasticity of the generic medicine estimated. RESULTS: Brand and price were the most important attributes. Even in the homogenous target group, five clusters with characteristic preferences, price elasticity and socioeconomics background were detected. Approximately half of the respondents were strongly price sensitive. Among all the respondents, the price elasticity of a generic OTC medicine was from -1.34 to -0.69 at the discount range of 20-60%. Even positive price elasticity was detected. In the clusters with negative price elasticity, discount of 4-42% were required to make the generic medicine equally preferred with the branded one. In comparison with the results of our corresponding study conducted before the launch of generic substitution leading to common interest in generic medicines and medicine costs in Finland, patients'  awareness of generic medicines had increased, attitudes towards them were more favorable, and they seemed to purchase OTC medicines more independently. CONCLUSIONS: The study provided novel information on the concomitant effects of brand, price and other essential product attributes on the patients’ choice of an OTC medicine. ACA proved to be a useful tool in the research of patients' and patient groups' preferences.