Background Psychological processes in bipolar disorder are of both clinical and theoretical importance. Aims To examine depressogenic psychological processes and reward responsivity in relation to different mood episodes (mania, depression, remission) and bipolar symptomatology. Method One hundred and seven individuals with bipolar disorder (34 in a manic/hypomanic or mixed affective state; 30 in a depressed state and 43 who were euthymic) and 41 healthy controls were interviewed with Structured Clinical Interview for DSM–IV and completed a battery of self-rated and experimental measures assessing negative cognitive styles, coping response to negative affect, self-esteem stability and reward responsiveness. Results Individuals in all episodes differed from controls on most depression-related and reward responsivity measures. However, correlational analyses revealed clear relationships between negative cognitive styles and depressive symptoms, and reward responsivity and manic symptoms. Conclusions Separate psychological processes are implicated in depression and mania, but cognitive vulnerability to depression is evident even in patients who are euthymic.