Background. Published studies of emotional processing and cognitive style in bipolar disorders tend to have small sample sizes or use non-clinical samples. Larger clinically representative studies are needed.Method. Self-esteem, dysfunctional attitudes and personality style were compared in unipolar (N=16) and bipolar disorder (N=77); and then investigated in the different phases of bipolar disorder (remitted=26; depressed=38; hypomanic=13). One-year outcome was assessed in 36 bipolar subjects.Results. Unipolar subjects and bipolar subjects differed significantly in their mean levels of negative self-esteem (unipolar=15·5; bipolar=12·7; PPPConclusions. There are similarities in the cognitive style of individuals with unipolar as compared to bipolar disorders. Cognitive style in hypomania represents a phase between remission and depression rather than the polar opposite of depression. The implications of these findings are considered for psychological and neural network models.