Objective: Cognitive impairment in elderly bipolar patients persists during euthymic state, yet the aetiology of such impairment is not well understood. The objective of this study is to identify factors contributing to cognitive impairment in elderly patients with bipolar disorder. Method: 119 older patients (age > 60) with bipolar I or II disorder in a euthymic state were extensively tested on cognitive functioning including attention, memory, visuoconstruction, executive function and verbal fluency with regard to potential risk factors. Results: Regression analysis shows that health related factors, medication and illness characteristics are associated with cognitive impairment in several cognitive domains: attention, memory, visuoconstruction, executive function and verbal fluency. More vascular burden factors are related to poorer outcome of cognitive functioning. Patients with lithium pharmacotherapy performed worse compared to those with other mood stabilizers, but this was no longer significant in multivariate analysis. Conclusions: In elderly bipolar patients, more vascular risk factors and more hospital admissions are associated with more cognitive impairment. © 2010 Elsevier B.V. All rights reserved.