In recent years, we can observe a turn to more empirical research in comparative constitutional law. This research is being conducted both by legal scholars and by political scientists. The paper has a two-fold aim. First, it gives an overview of the state of the art of empirical research in comparative constitutional law. It focuses on two main areas – the study of constitutional design, on the one hand, and research on judicial decision-making in the domain of constitutional law, on the other. Second, it provides a critical assessment of this scholarship. In particular, it argues that most of the studies on constitutional design do not adequately address the issue of unobserved variable bias. While these studies are still valuable in order to advance empirical research within comparative constitutional law, they should not be used without caution as possible basis for policy recommendations.