IntroductionCurrently, cognitive behavior therapy (CBT) targets multiple cognitive processes. However, only a few studies have focused on the interaction among these processes. Preliminary studies have identified a moderation effect of rumination on the link between thought content and emotional difficulties, and a mediation effect of ruminations on the link between mindfulness and emotional difficulties. MethodWe recruited 236 participants (185 women) who consented online to participate by choosing to either continue with the study or decline to proceed. They completed a battery of questionnaires online, namely Positivity scale, General Health Questionnaire, Rumination Response Scale, Five Facet Mindfulness Questionnaire and Cognitive Fusion Questionnaire. ResultsAll cognitive processes were significantly correlated with emotional distress. Step-by-step linear regression analysis revealed that positivity, cognitive fusion and brooding were significant independent predictors of emotional difficulties. Bootstrapping analysis confirmed that cognitive fusion and brooding mediate the link between mindfulness and depression and anxiety-insomnia. They also demonstrated that cognitive fusion moderates the link between positivity and depression but not anxiety-insomnia. ConclusionCognitive processes interact with each other. Taken together, these results suggest that combining cognitive interventions is not useful and that different cognitive interventions may be selected depending on the patient's profile.