Objective: Studies on normal children revealed the fact that they could understand and use embodied metaphorical expressions since they started language learning. Method: In this study, two groups each including ten children aged four and a half to five made the sample. One group consisted of normal children and the other consisted of children with William syndrome. This study aimed to get a better knowledge of this disease “William syndrome” and to compare the cognitive knowledge of both groups. As the children with William syndrome were very sociable, they did not have any problem with every day conversation; however, understanding metaphorical expressions was the only issue they had. This experimental-descriptive study retrieved from the Bialka-Pikal (2003) has been carried out without any changes of variables. Result: This study showed that children with William syndrome had minimum metaphorical understanding. In other words, they had relative understanding of metaphorical structure. In this group, the metaphor of taste with 1.50 and the metaphor of form with 0.4 received the highest and the lowest scores, respectively. Conclusion: In terms of using metaphorical expressions, the findings indicate that children with William syndrome do well in filling in the blank exercises and there is a slight difference in their performance in comparison to normal children. However, they are far weaker than normal children in terms of recognizing sameness in dual test cards.