Over the last two decades, the importance of executive functions in successful adaptive living has been increasingly recognized. Hence, investigation of executive functioning has become a core component of neuropsychological assessment. At present, correct identification is seen as crucial to ensuring adequate treatment, compensation and support. It is argued here that, in the medico-legal arena especially, but also in clinical practice, neuropsychological assessment may rely too heavily on data derived from office-based tests of executive functioning both for the identification of deficits and also for the prediction of their real world consequences. This paper discusses the discriminant and ecological validity of such tests and implications for the future assessment of executive functioning. Additionally, the importance of reliable behavioural observations, made in more ecologically valid environments than purely the consulting room is stressed.