Empirical studies on people's moral attitudes regarding ethically challenging topics contribute greatly to research in medical ethics. However, it is not always clear in which ways this research adds to medical ethics as a normative discipline. In this article, we aim to provide a systematic account of the different ways in which attitudinal research can be used for normative reflection. In the first part, we discuss whether ethical judgements can be based on empirical work alone and we develop a sceptical position regarding this point, taking into account theoretical, methodological and pragmatic considerations. As empirical data should not be taken as a direct source for normative justification, we then delineate different ways in which attitudes research can be combined with theoretical accounts of normative justification in the second part of the article. Firstly, the combination of attitudes research with normative-ethical theories is analysed with respect to three different aspects: (a) The extent of empirical data which is needed, (b) the question of which kind of data is required and (c) the ways in which the empirical data are processed within the framework of an ethical theory. Secondly, two further functions of attitudes research are displayed which lie outside the traditional focus of ethical theories: the exploratory function of detecting and characterising new ethical problems, and the field of 'moral pragmatics'. The article concludes with a methodological outlook and suggestions for the concrete practice of attitudinal research in medical ethics.