Previous studies have found that understanding another person's mental states is a requirement for effective responding to that person. This study examined whether effective responding also requires selecting a relevant mental state of another person. Using a hypothetical persuasion paradigm, we investigated if late 4-and 5-yearolds (N 0120) could present information to counter a receiver's opposition. For example, a boy is attempting to persuade his mother to let him have a bird. If the mother objects to her son having the bird because bird is noisy, then the boy should ask her to have a quiet bird. Presenting appropriate information (e.g., a quiet bird) was found to be more difficult when the person had plural beliefs (e.g., a bird would be clean and noisy) and children had to select the source of opposition (e.g., a bird would be noisy). This suggests that selecting an appropriate mental state of another person is necessary for effective responding. Contingency and developmental analyses revealed that children could present appropriate information only when they could select the source, indicating that the ability to select an appropriate mental state is a key factor in responding effectively to others.