Most children's speech difficulties are "functional" (i.e. no known sensory, motor or intellectual deficits). Speech disorder may, however, be associated with cognitive deficits considered core abilities in executive function: rule abstraction and cognitive flexibility. The study compares the rule abstraction and cognitive flexibility of children with speech disorder and typically developing controls. Three groups of five-year-old children (typically developing, consistent atypical speech disorder and inconsistent speech disorder) were assessed on the Flexible Item Selection Test (Jacques and Zelazo, 2001). Children were shown a set of three cards and asked to select two that matched on one dimension (selection 1: abstraction). Children were then asked to select a different pair of cards that matched on another dimension (selection 2: flexibility). The children with consistent atypical speech disorder performed worse than the other two groups on selections 1 and 2. The children with an inconsistent speech disorder performed similarly to their typically developing peers. Children who use consistent atypical error patterns have difficulties with rule abstraction and flexibility that are not confined to the linguistic system. The results are discussed in terms of the deficits underlying different types of speech disorders. (Contains 4 tables.)