Studies of adults who have been diagnosed with, and treated for, bipolar disorder have shown that these patients exhibit impairment on measures of executive functioning. However, it is unclear whether executive dysfunction precedes the diagnosis of bipolar illness, or develops subsequent to its onset. Moreover, investigators have failed to control for the effects of premorbid attentional problems on cognitive performance in these patients. The present authors explored these questions using data from a longitudinal prospective study of individuals at risk for major mood disorder. Results revealed that 67% of participants who met criteria for bipolar disorder in young adulthood showed impairment on the Wisconsin Card Sorting Test (WCST) when they were assessed during adolescence, as compared with 17% of individuals with no major mood diagnosis, and 19% with unipolar depression. This association between performance on the WCST and bipolar illness was not accounted for by high rates of premorbid attentional disturbance. In fact, among participants with early attentional problems, only those who ultimately developed bipolar disorder exhibited impairment on the WCST. Early attentional problems that preceded unipolar depression or no mood disorder were not associated with executive dysfunction.