Currently, there is a major health problem in our society, which partially is the result of an insufficient level of physical activity. Despite existing intentions, people sometimes fail to turn them into action and engage in physical activity. This intention-behavior gap provides a framework for the topic under study. Fitness apps offer a way to assist and support people in implementing physical activity in their daily routine. Therefore, this paper investigates the influence of user diversity on motives and barriers to fitness app use. For this purpose, a choice-based conjoint study was conducted in which 186 subjects were asked to repeatedly choose their favorite between three fictitious constellations of fitness apps. The apps were configured based on selected attributes. Differences in decision-making between men and women, exercisers and non-exercisers, as well as influences of certain personality dimensions and motivational types have been found. The results provide important clues that may help to customize fitness apps to specific user groups and for further research.