The purpose of this thesis is to investigate the effects of personality traits on stress intervention, based on an exploration of empirical literature with multiple methodologies. Here, personality traits are defined by Costa & McCrae’s Big Five: Neuroticism, Extraversion, Openness to Experience, Agreeableness and Conscientiousness. Two types of stress intervention are explored: Cognitive Behavioural Therapy (CBT) and Mindfulness Based Stress Reduction (MBSR). Both types of intervention are among the most frequently used therapies in stress reduction in the Western world today. Through an exploration of literature on CBT and MBSR, the intention of the thesis is to illustrate what effects two types of stress intervention have in relation to specific personality traits. It is found that certain personality traits predict individual differences in both stress exposure, the unfolding of the stress response and coping with stress. Through intervention, here explored by CBT and MBSR, the individual may obtain new strategies for handling stress. This is the case for both CBT and MBSR due to changes in cognition.Since the experience of stress is subjective to the individual, depending on a number of both internal and external factors, where mental, physical, environmental and genetic resources are involved, the concept of coping is additionally explored related to personality and perceived stress. Research into the harmful consequences of stress shows how acute and prolonged stress can result in physiological, cognitive, behavioral and social deficiencies, and may contribute to the development of disorders ranging from depression to cancer and immunological dysfunction (Leahy, 2002). The exploration shows that the way in which stressful events are handled is therefore crucial to the further outcome of events, and thus the individual's coping is predominantly relevant to the understanding of which factors contribute to increased or reduced levels of stress. The structure of the thesis is: three main theoretical sections and one overall discussion. Here the concept of stress is reviewed through both neurosocial and cognitive lenses, exploring the historical development from homeostasis (Cannon, 1929) to allostasis (Sterling & Eyer, 1988; McEwen, 1998a), cognition and emotion (Lazarus, 1966) through structural changes in the brain. Following this, a theoretical understanding of CBT and MBSR leads on to the general discussion of the influence of personality traits in stress intervention where the research question “How do prominent personality traits affect the individual's use of, as well as benefits from CBT and MBSR?” will be discussed.Concluding remarks point out that individual differences in personality lead to differences in the individual experience and use of therapeutic intervention. Here the personality traits: Extroversion, openness to experience, agreeableness and conscientiousness are all personality traits, where high levels facilitate a positive therapeutic result (Ogrodniczuk, Piper, Joyce, McCallum & Rosie, 2003). Mindfulness intervention facilitates adaptive psychological functioning. Despite existing methodological limitations within each body of literature, there is a clear convergence of findings from correlational studies, clinical intervention studies, and laboratory-based, experimental studies of mindfulness—all of which suggest that mindfulness is positively associated with psychological health, and that training in mindfulness may bring about positive psychological effects. These effects range from increased subjective well-being, reduced psychological symptoms and emotional reactivity, to improved regulation of behavior.The explored empirical data has contributed to the understanding of how distinctive features of individuals are crucial in relation to the unfolding of the stress response, and how these features moreover have an influence on the effect of cognitive behavioural therapy and mindfulness intervention (exemplified by the Mindfulness Based Stress Reduction).Further studies should be made regarding exploration of how dimensional personality traits can contribute with useful information in a clinical context. It would be interesting to investigate aspects of the therapy process that can mediate the effect of the different personality dimensions on the treatment result. This work could possibly help clarify how different personality characteristics affect the outcome of the therapy and how the treatment can be tailored to the client's strengths and weaknesses.