In this study, we analyzed the economic impact of one-year healthcare and non-healthcare resources utilization by patients with dementia of Alzheimer's disease (AD) under usual medical practice in Spain. A one-year, prospective, naturalistic, multicenter cohort study was designed to recruit patients with mild, moderate to severe, and severe AD according to Clinical Dementia Rating scale: the ECO study. Healthcare resources (medical visits, drugs and concomitant treatments, complementary and diagnostic tests, institutionalization and use of home-nursing facilities) and non-healthcare resources (inventory materials, consumables, professional and non-professional caregivers' time for care and supervision) were recorded and valued at 2006 prices. A total of 560 patients with possible/probable AD by DSM-IV-NINCDS-ADRDA criteria were included in the study: 68% women, 77 ± 6 years old, 29% treatment naïve. Monthly average cost per patient was EURO1,425.73, and increased 10.08% at the end of the study (baseline monthly cost; EURO1,316.22). Non-healthcare costs EURO1059.00, 74.30% of total cost) decreased EURO4.30/month (0.40%) at the end of the year, while healthcare costs, which presented a total average of EURO366.66, grew by EURO136.94 in the period (54.06%), mainly due to cost of drugs, nursing home utilization, and institutionalization. The 87.26% of the overall cost (EURO1,244.22) was not financed by National Health Service (NHS), and the majority of this cost corresponded to caregiver-associated cost. The caregiver's total burden represented 70.86% of the overall cost-of-illness. In conclusion, monthly overall mean cost of dementia of AD type was high in Spain (EURO1,412.73). Almost 88% of the cost-of-illness is funded by the patient's own family, adding a financial burden to the suffering of these families.