Accessible summary People with Down syndrome and intellectual disabilities are more likely to get dementia when they are older. This is an illness where people become forgetful and confused. Sometimes people with Down syndrome start to behave strangely at the start of the illness. They have difficulties solving problems or have changes in their behaviour. This is called executive functioning. We looked at some different tests to see whether they could help us understand whether someone was having problems with their executive functioning skills. We found that the tests can be useful and that we should be using them with more people. We think that we need to wait for a longer time before finding out whether they can tell us whether someone has dementia or not. This is important for people with intellectual disabilities as we need to find the right tests to help us diagnose dementia as early as possible. Summary The following article details a piece of service development work undertaken as part of the Plymouth Down Syndrome Screening Programme. The work aimed to review the use of three measures assessing executive functioning skills used within the Programme as well as with people without Down syndrome. Three tasks assessing executive functioning (the Weigl, Cats and Dogs, and verbal fluency task) were evaluated. The Weigl task was removed from the Programme and analyses due to floor effects and difficulties in administration. Correlation analyses showed relationships between the Cats and Dogs task and two other measures, cognitive skills as reported by carers and object memory. No relationships were found between the verbal fluency task and other measures. A full consideration is given to these findings, and implications for future practice are considered. Further data are needed to make full conclusions about the value of the tasks in predicting dementia in people with intellectual disabilities and people with Down syndrome. Further recommendations concerning the development of the assessment of executive skills are also considered.