Bipolar disorder (BPD) is a serious mental illness that affects children and adolescents at a rate similar to that seen in adults. Extremely little is known, however, about cognitive functioning in childhood and adolescent BPD. The present study represents an initial effort to examine executive functioning in adolescents with BPD who are in a manic or mixed mood state, by collecting data from caregivers about the participants' performance on everyday tasks thought to be mediated by executive functioning abilities, using the Behavior Rating Inventory of Executive Function. In comparison to healthy volunteers, adolescents with BPD exhibited significant elevations across all of the measured functional domains. These elevations were evident even in adolescents with BPD who did not have comorbid ADHD, although they were most prominent in those with comorbidity. The findings suggest that adolescents with BPD have functional deficits on tasks requiring executive functioning skills that are not explicable solely on the basis of comorbid ADHD.