In various domestic mammals, smaller breeds tend to have proportionally larger teeth, whereas this is not a universal trend across mammals. This suggests that body size can evolve faster than tooth size, leading to the prediction that tooth-body size scaling differs among closely related versus distant taxa. Here, we test this pattern in a new computed tomography (CT)Skriffer Utgitt au det Norske Vidensk-Akad scan dataset on 302 adult domestic rabbits of various breeds (maxilla and mandible) and compare this to 198 literature data from 20 nondomestic lagomorph species (maxilla only). Skull or mandible length served as body size proxies. The allometric scaling of the length of the cheek tooth row and the diastema, as well as the jaw width, with these proxies and with each other was investigated. In domestic rabbits, there is a negative allometric scaling between tooth row length and body size, that is, smaller animals have relatively larger teeth. Similar patterns appear within some wild lagomorph species, while across species, tooth row length and body size scale isometrically. These findings add to reports on allometric growth in domestic species. As the seeming advantage of disproportionately more chewing surface in smaller species is apparently lost over time, the postulate of an optimal tooth row size for an organismal design emerges, for which there is currently no theory. Possibly, veterinary experiences that dental problems are particularly frequent in small domestic breeds with relatively larger teeth might provide leverage for such a concept. Studies on the physiological effects of differences in relative tooth size between breeds are warranted.