Providing accurate and detailed statements in police interviews can be challenging, especially for children. After reviewing the challenges relevant to the formation, maintenance and recall of memories, study 1 reviewed the guidance available to police interviewers questioning children in Germany and placed it in an international context through comparison with European manuals and the United States manual. As guidance was found to be limited, study 2 compared primary school-aged children's and adults' understanding of police interviews. Six- and 7-year-old-children were identified as the most vulnerable age group who tended to lack very basic knowledge. Study 3 introduced a live intervention to improve 6- and 7-yearolds' knowledge of how their behaviour could impact on statements in police interviews. This intervention was found to be effective for this age group. Study 4 replicated this finding with 9- and 10-year-old children and additionally suggested that this age group's understanding of police interviewer behaviours could be improved through the same live intervention. In contrast, study 5 suggested that 6- and 7-year-old children's knowledge of police interviewer behaviours could not be improved through the previously used live intervention or an analogous video intervention delivered by a mock police man. Study 6 compared the effectiveness of these two delivery methods of the intervention – live and video – and suggested that, for 8- to 10-year-old children, there was no difference in effectiveness between both delivery methods in improving the knowledge of interviewer and interviewee behaviours for up to a week. Taken together, these findings suggest that, while children's limited understanding of police interviews might be an underlying factor that impairs their ability to testify, only the understanding of older children can be improved for interviewee and interviewer behaviours, while younger children's knowledge can only be improved for interviewee behaviours.