Assessment of mindfulness is essential to understanding its relationships with psychological functioning. Currently, mindfulness is most often assessed with self-report questionnaires. Although additional work is required, mindfulness questionnaires have reasonable psychometric properties and are making important contributions to the understanding of mindfulness and its effects on health and wellbeing. For example, measurement of mindfulness as a multidimensional construct shows that present-moment awareness can be unhelpful unless accompanied by a nonjudgmental, nonreactive stance; moreover, nonjudgment and nonreactivity may be only weakly related to present-moment awareness in people with no meditation experience. Differences between psychological and Buddhist conceptions of mindfulness, though often a source of criticism of mindfulness questionnaires, are argued here to be inevitable and not necessarily problematic.