The cognitive model of obsessions (Rachman, 1997, 1998) proposes the escalation from normal intrusive thought into clinical obsession begins with the appraisal of thoughts as being significant or dangerous. The cognitive theory of obsessions also posits through targeting and dismantling maladaptive thought related beliefs and thought control strategies, one can reduce the frequency of and discomfort associated with obsessive thoughts. The current study first set out to obtain additional empirical support for the proposed relationship between maladaptive thought related beliefs, thought management strategies, and obsessive thinking. Next, this study explored the potential impact of targeting and altering maladaptive thought related beliefs and thought management strategies, through mindfulness-based training (thought acceptance), in comparison to relaxation-based training (thought control). Finally, this study assessed which, if any, participant characteristics were associated with positively responding to mindfulness training. Results highlighted the strong relationship between maladaptive thought related beliefs, thought management strategies and obsessive thinking, with mindfulness mediating the relationship between maladaptive thought related beliefs and obsessive thinking. Research results also lend support for the potential efficacy of both mindfulness as well as relaxation based training, for the treatment of obsessive thinking. Participants assigned to both conditions exhibited decreased obsessive thinking as well increased positive mood state and decreased maladaptive thought related beliefs. Process related analysis uncovered a significant relationship between decreased maladaptive thought related beliefs and decreased obsessive thinking for the mindfulness condition, providing initial evidence for changes in meta-cognitive beliefs as an active ingredient in mindfulness training. In contrast, a significant relationship between decreased maladaptive thought related beliefs and decreased obsessive thinking was not found for the relaxation condition. Finally, when assessing participant characteristics associated with positively responding to mindfulness training, level of obsessive thinking predicted self reporting to have obtained a significant benefit from engaging in mindfulness training, with study participants experiencing higher levels of obsessive thinking interpreting the mindfulness intervention as more beneficial than study participants who experienced lower levels of obsessive thinking. These findings offer initial evidence that mindfulness training may be a useful treatment approach, in targeting and altering maladaptive thought related beliefs, for the treatment of obsessive thinking. / text