Introduction: Atrial fibrillation might increase the risk of dementia. We aim to test the hypothesis that dementia could reclassify the actual risk of stroke and death predicted by the CHA2DS2-VASc in patients with atrial fibrillation (AF). Methods: A prospective study performed in a specific health care area. Results: From our health care area (n = 348,985), throughout 2013, AF was codified in 7,990 (2.08%). Mean age was 76.83 ± 10.5, mean CHA2DS2-VASc = 3.5, 4,056 (50.8%) were females and 287 (3.6%) were diagnosed to have dementia. Patients with dementia were older and presented a higher rate of all the components of the CHA2DS2-VASc-expect vasculopathy. Differences in overall mortality were observed but not in stroke and haemorrhagic events. After propensity score matched analysis, dementia was independently associated with all-cause mortality. Addition of dementia to CHA2DS2-VASc reclassified 7.7 and 16.6% of the cohort with regard to thromboembolic events and death risk respectively. Conclusions: Patients with dementia presented a more adverse risk profile, with significant differences in all-cause mortality.