Sustained attention deficits are proposed to be both state and trait indicators of bipolar disorder. The nature of these deficits and their association with medication and symptoms is not clear yet. The aim of this study was to investigate the impairments in various components of sustained attention task in euthymic and manic patients and was to investigate the relationship between the deficits in the manic state and medication effects. The performances of 37 manic patients, 34 euthymic patients with bipolar disorder and 34 control subjects on eight scores from Conners' CPT II, reflecting three different dimensions of sustained attention were compared. Similar to some recent findings, euthymic patients had decreased target sensitivity (omission errors) and response time inconsistency. The increased false responding (commission errors), perseveration and vigilance deficits were prominent in the manic patients. These state dependent impairments could not be explained by the impact of medication. In contrast, the exacerbation of seemingly trait-related impairments in the manic state can be at least partly explained by the impact of pharmacological therapy.