The Buddhist construct of mindfulness is a central element of mindfulness-based interventions and derives from an age-old systematic phenomenological program to investigate subjective experience. Recent enthusiasm for "mindfulness" in psychology has resulted in proliferation of self-report inventories that purport to measure mindful awareness as a trait. This paper addresses a number of intractable issues regarding these scales, in general, and also specifically highlights vulnerabilities of the adult and adolescent forms of the Mindfulness Attention Awareness Scale. These problems include (a) lack of available external referents for determining the construct validity of these inventories, (b) inadequacy of content validity of measures, (c) lack of evidence that self-reports of mindfulness competencies correspond to actual behavior and evidence that they do not, (d) lack of convergent validity among different mindfulness scales, (e) inequivalence of semantic item interpretation among different groups, (f) response biases related to degree of experience with mindfulness practice, (g) conflation of perceived mindfulness competencies with valuations of importance or meaningfulness, and (h) inappropriateness of samples employed to validate questionnaires. Current self-report attempts to measure mindfulness may serve to denature, distort, and banalize the meaning of mindful awareness in psychological research and may adversely affect further development of mindfulness-based interventions. Opportunities to enrich positivist Western psychological paradigms with a detailed and complex Buddhist phenomenology of the mind are likely to require a depth of understanding of mindfulness that, in turn, depends upon direct and long-term experience with mindfulness practice. Psychologists should consider pursuing this avenue before attempting to characterize and quantify mindfulness.