Individuals with the rare genetic disorder, Williams syndrome, have an unusual cognitive profile with relatively good language abilities but poor non-verbal and spatial skills. This study explored the interaction between linguistic and spatial functioning in Williams syndrome by investigating individuals' comprehension of spatial language. A group of 17 individuals with Williams syndrome and a control group of typically developing children were given two types of picture-matching task in which they were asked to select a picture to match a spoken sentence describing the spatial relation between two items. In the first task this matching could be done on the basis of existing semantic knowledge. In the second, we argue that a mental representation of the spatial relations was required. Results demonstrated that individuals with Williams syndrome were selectively impaired on the second task relative to controls. The study therefore provides support for previous work demonstrating impaired comprehension of spatial language in this population. Furthermore, the results suggest that such impairments reflect a fundamental problem with processing spatial descriptions rather than merely a poor understanding of the semantics of spatial terms, which in turn has implications for the interaction between spatial abilities and language processing in general. (Contains 3 figures, 1 tables and 1 note.)