This paper presents and discusses the psychological interventions that are primarily based oil the development Of mindful awareness as a psychotherapeutic tool. Mindfulness based psychological interventions are defined and situated in their historical context, in the larger perspective of the evolution of psychotherapies in the Western world in the last two decades. A special focus is given to mindfulness based stress reduction (MBSR, Kabat-Zinn, 1982) and to mindfulness based cognitive therapy (MBCT Segal, Williams & Teasdale, 2002). The structure and core elements of these interventions are presented. Then, we examine their effectiveness ill improving psychological and physical well-being. In the next section, we speculate about the underlying psychological mechanisms that might account for the effects of mindfulness based interventions. Special attention is devoted to the cognitive processes underlying emotion regulation and self-awareness. Finally, we examine how a first person approach might contribute to the understanding of mindfulness based interventions