Individuals with bipolar disorder (BD) may exhibit attentional deficits, however, the extent of impairment and long-term fluctuations in performance in attention are relatively unknown. We investigated the relationship between sustained attention and affective symptoms over time among BD patients. We also examined whether global differences in attentional capacity differed among BD versus normal comparison (NC) subjects. Participants included 106 outpatients with BD and 66 NC subjects who were administered symptom rating scales and a measure of sustained attention (Continuous Performance Test- Identical Pairs). Measures were repeated 6, 12, and 26 weeks post-baseline. Compared to NC subjects, participants with BD showed impairment in sustained attention across time. Within patient increases in manic symptoms were associated with increased false alarms; both manic and depressive symptoms were associated with worse discrimination. Neither manic nor depressive symptoms were related to hit rates. Our results indicate that the ability to inhibit a response to near miss stimuli (i.e., those that are close to but not identical to the target) is globally impaired among BD patients relative to NC subjects, as well as state-dependent, covarying with affective symptoms. Psychosocial interventions requiring high levels of attentional capacity may need to be adapted according to patients' current symptomatology.