Diabetes mellitus (DM) is a chronic medical condition that is dependent upon patients self-caring and managing their condition to achieve optimal control. Adherence to medical therapy, making decisions related to lifestyle changes, and self-treating hypoglycaemia for example, require planning and organisational skills that are under the control of a specific domain of cognitive function known as executive function. Executive function has been shown by functional imaging studies such as magnetic resonance imaging to be under the influence of the frontal and prefrontal cortical system. It is now recognised that even in subjects with apparently normal cognition, DM may be associated with impaired executive function (IEF). The exact cause of IEF in DM is still not fully understood. However cerebral microvascular disease and chronic dysglycaemia have been postulated as possible factors contributing to functional neuronal dysfunction leading to IEF. IEF may adversely affect patients abilities to self-manage their diabetes care, potentially cause worsening glycaemic control and difficulty managing risk factors. Several bedside assessment tools to screen for IEF are currently available and have been shown to correlate with functional status. However, more studies are needed to validate these tests against diabetes self-care assessment tools. Until then, clinicians and healthcare workers managing patients with DM should be aware of the potential for IEF in their patients as specific behaviour and education intervention may be needed to help manage patients with diabetes and IEF.