In modern French dialectology, the critical usage of text data for the appropriate description of diatopic (regional) elements of national or regional varieties of Frenchthough crucialis hardly commented in scientific discourse. The paper offers an overview on the main corpora that are, or could be used for the lexical study of diatopicisms in contemporary French in the northern part of the francophone world, whether it be traditional, mostly literary corpora, journalistic texts, recent web corpora, or 'oral' corpora. The author examines their suitability for identifying diatopicisms with their spatial distribution in a francophone perspective, presents current methods of text analysis, and points out various problems related in particular to text location, regional annotation, discourse genres and treated subjects, but also to formal compatibility, text size and practical access. The article therewith underlines the need, in a close future, of comparable data for the different varieties in the francophone world in order to enhance the description of diatopic variation in modern French.