Constitutional comparison involves a range of different modes of comparison – that is, comparison that is ‘genetic’ or ‘genealogical’, deliberative or discourse-oriented, doctrinal, empirical, reflective and moral-cosmopolitan in scope, as well as hybrid in nature. Each of these modes has ‘thinner’ and ‘thicker’ variants, and a somewhat different focus, or concern to understand the constitutional history, arguments, doctrines, practices and experiences, or values, of other countries. Further, each implies a different geographic focus, or scope, and attention to comparative judicial decisions, legislative practices and social science sources. Some forms of comparison are also more methodologically demanding, than others. Empirical comparison in particular invites either ‘large n’ studies, or else, ‘smaller n’, qualitative studies that draw on rigorous principles of case-selection. One of the aims of the article is also to explain these principles, while at the same time arguing for a robust and realistic approach to their application.