The article studies metaphor and metonymy comprehension in children with Williams Syndrome (WS), who exhibit relatively well developed vocabulary and syntax against a background of rather poor cognitive abilities. This is one among only a handful of studies investigating metaphor understanding in children with WS, and the first to include metonymy. In the course of the study, ten children with WS were tested using novel tasks involving comprehension of metaphor and metonymy. The results were compared with those of eleven typically developing children. The results of metaphor comprehension achieved by the children with Williams syndrome were significantly lower than in the control group, whereas understanding of metonyms was found to be consistent with the children’s receptive vocabulary. In conclusion, the higher scores for metonymy comprehension may be accounted for by metonyms being a part of vocabulary (handled as synonyms) and consequently processed with relative ease by children with WS. The reason why metaphor understanding is affected more severely is that metaphor involves cognitive mechanisms that lie beyond language, and these do not develop normally in WS. These observations serve to identify limitations in the linguistic development of children with Williams Syndrome.