Adults with an intellectual disability (ID) are often considered poor witnesses; however, this may depend on the type of questions asked during investigative interviews. We examined the impact of four different types of misleading questions commonly used in interviews. These questions varied in their specificity, presumptive knowledge and structure (open or closed). Forty-one adults with a mild ID watched a short film; they were then interviewed about what had happened. Half of the questions contained misleading information. In a later recognition test, participants showed a misinformation effect: they correctly recognised more items about which they had received control information than the items about which they had received misleading information. Closer inspection of the data revealed that both closed and open presumptive questions generated the largest misinformation effects. These findings highlight the vulnerability of adults with an ID to misleading questions, specifically those that presume certain information to be true. Copyright © 2013 John Wiley & Sons, Ltd.