OBJECTIVES: To assess the economic burden of moderate Alzheimer´s Disease (AD) and to analyze the impact of depression, from the societal perspective. METHODS: IDEAL is an epidemiological, prospective and multicentric study in which 1,071 patients from 180 investigators in Spain, with moderate AD and available information on resources were assessed. Resources consumption was assessed in a cross-sectional way at the end of the study. The following resources were included in the analysis: healthcare (medication: anti-Alzheimer, neuroleptics and anti-depressive drugs) and non-healthcare direct costs (formal care and social services: institutionalization and day care center attendance) and  indirect costs (caregivers loss of productivity). Costs are expressed in euros 2007. The cognitive and functional status were measured by the Mini-Mental State Examination (MMSE) and Barthel Index, respectively. Patients were grouped taking into account the score obtained in the depression Cornell Scale (cut-off-point: ≥8). RESULTS: Depression was present in 52% of the patients. The average monthly cost per patient was €1043 and €653 in patients with and without depression, respectively. Non-health care direct costs and the caregivers loss of productivity were the most important cost categories. In patients with depression, 56%, 34% and 10% were attributable to non-health care direct costs, productivity loss and drug costs, respectively. In comparison, in patients without depression, the same distribution costs were 61%, 25% and 14%. The cost of productivity loss is more than doubled in the depression patient cohort. Patients with depression showed a higher and significant cognitive impairment, through MMSE scores: 14.7 (±4.7) in depressed patients and 15.2 (±4.9) in non-depressed patients. The same finding was observed in the daily life activities measured by the Barthel Index: 68.2 (±22.7) and 81.1 (±19.9) in patients with and withour depression. CONCLUSIONS: Adequate management of depression in patients with moderate AD would have a positive impact on societal resource consumption.