In the last decade, a surge of interest has been directed towards the empirical investigation of the concept and applications of mindfulness. If one considers the increasing evidence about the clinical benefits and the psychological and neurobiological correlates of current mindfulness based interventions (MBIs), it is surprising that significantly lower effort has been directed towards the achievement of a consensus about an unequivocal operationalization of mindfulness within modern Western psychology. Accordingly, the present review aims to summarize traditional and current perspectives about mindfulness, to discuss the extent to which modern definitions of mindfulness differ from more traditional definitions and, more specifically, the limitations of current questionnaires that are thought to measure mindfulness levels, and to provide suggestions for future research on this topic. In sum, according to authors well versed in the original Buddhist literature, from which several MBIs are overtly or implicitly derived, modern attempts to operationalize mindfulness have consistently failed to provide an unequivocal definition of mindfulness, which takes into account the complexity of the original definitions of mindfulness. Although the concept of mindfulness remains elusive and difficult to capture by means of modern self-report questionnaires, however, several alternatives exist that could shed light on closely related constructs, which could deepen our understanding of mindfulness and that could lead to the development of new, not yet considered, categories of psychological effects associated with mindfulness training.