The recent introduction of the WHO cytology classification of pancreatobiliary tumours aimed to improve the diagnosis and management of these tumours. The present paper briefly describes the methods of diagnosis. Emphasis is then put on a detailed comparison of the previous Papanicolaou classification and the new WHO classification and description of the changes brought about by the introduction of the WHO classification. In the last part of the paper, we present interesting cases from our practice illustrating possible diagnostic pitfalls of cytological evaluation.