This Topical Review provides an overview of the dielectric properties of a variety of organic charge-transfer salts, based on both, data reported in literature and our own experimental results. Moreover, we discuss in detail the different processes that can contribute to the dielectric response of these materials. We concentrate on the family of the one-dimensional (TMTTF)2X systems and the two-dimensional BEDT-TTF-based charge-transfer salts, which in recent years have attracted considerable interest due to their often intriguing dielectric properties. We will mainly focus on the occurrence of electronic ferroelectricity in these systems, which also includes examples of multiferroicity. ; Comment: 34 pages, 24 figures