Measures of sentence recall and past tense marking were used to examine the similarities and differences between children with Attention Deficit/Hyperactivity Disorder (ADHD), children with specific language impairment (SLI), and typically developing (TD) children. Both SLI and ADHD group means for sentence recall tasks were significantly lower than the TD control group (SLI [is less than] ADHD [is less than]TD). In contrast, limitations in past tense marking were characteristic of the SLI group (SLI [is less than] ADHD=TD). Frequent affix omissions or bare stem errors (e.g. "the girl colour the picture"; "the girl fall in the net") differentiated the SLI group from the other two groups. Over-regularization errors (e.g. "the girl falled into the net") did not (SLI=ADHD=TD). Clinical implications are discussed.