Comparative law is a field of study that examines legal systems to gain insights for both theoretical and practical purposes. It encompasses the comparison of legal systems to identify their similarities and differences, the systematic analysis of how multiple systems address specific legal problems, and the exploration of methodological challenges in comparative research and the study of foreign law. A key aspect of comparative law involves the traditional comparison de lege lata and/or de lege ferenda, often aimed at identifying models for legislative reform at domestic, regional, or international levels. However, comparative law research frequently encounters methodological difficulties, particularly in establishing the tertium comparationis—the common reference point that enables meaningful comparison between legal rules or institutions. This chapter examines fundamental aspects of comparative law methodology, with a focus on the legal-dogmatic and functional approaches to comparability. It argues that, depending on the specific objectives of a research project, integrating elements from both approaches can offer a productive means of addressing methodological challenges in comparative law research.