© 2014 Japan Geriatrics Society. Objectives: The aim of the present study was to explore the magnetic resonance imaging correlates of the performance of instrumental activities of daily living (IADL) in patients with Alzheimer's disease combined with cerebrovascular disease. Methods: A total of 66 patients with Alzheimer's disease combined with cerebrovascular disease formed the study sample. Two regression models were constructed to find correlates of IADL. Model 1 only included clinical variables and model 2 included both clinical and magnetic resonance imaging variables. Results: In model 1, with IADL as the dependent variable, the Mini-Mental State Examination (MMSE) score, Physical Self-Maintenance Scale score at baseline and age were significant correlates accounting for 40.1% of the variance of IADL at baseline. MMSE score and age were also significant correlates of IADL at 6 months, accounting for 38.1% of the variance of it. In model 2, severity of white matter lesions, MMSE and Physical Self-Maintenance Scale scores at baseline significantly correlated with IADL at baseline, accounting for 52.1% of the variance of the dependent variables; severity of white matter lesions and MMSE significantly correlated with IADL at 6 months, accounting for 41.5% of the variance of the dependent variables. Conclusion: In patients with Alzheimer's disease combined with cerebrovascular disease, subcortical ischemic lesions might be significant contributor to the functional status.