This paper reports on a research project that investigated how library and information (LIS) professionals experience ethical dilemmas, with particular reference to the impact of new technologies, sources used to assist ethical decision-making, and the contribution case studies can make to ethical understanding and decision-making. Data was collected through interviews in Britain, Ireland and Australia with LIS professionals, educators, and representatives of professional bodies. The findings identify the main types of dilemma raised and discuss cases indicative of each type. They suggest that new technologies do not appear to change ethical principles but, when experienced in the workplace, substantially change the factors the professional has to evaluate. They also suggest that relevant codes of ethics are satisfactory on traditional library issues of access and confidentiality, but do not address the ethical challenges of current and potential digital environments. Professional associations appear more familiar with codes of ethics than practitioners although practitioners show high levels of ethical awareness, suggesting associations need to communicate more with their members and provide tools that are more useful in the workplace. Case studies are seen as a good way to educate and engage practitioners because of the complexity, conflicts and dynamism they can present.