A marked variability has been documented in the therapeutic approaches to diabetes by various countries, suggesting that the level of care currently delivered may not produce the expected health-related gains. We investigated quality of care indicators in a large, representative multiregional population-based cohort of people (the ARNO Observatory) living in four Italian regions (2 million inhabitants), assessing process indicators and hospital admissions as outcome indicators. The strength of this report is the population-based multiregional study design, which includes a great number of patients cared for by diabetes clinics and GPs. In this respect, we extend previous evidence limited to process indicators obtained in the setting of specialized clinics, pointing out widespread inadequacy of care provided by both diabetes clinics and GPs. In conclusion, this population-based study shows that the implementation of diabetes care guidelines is far from being satisfactory in Italy, consistent with what has been observed in other Western countries. A greater adherence to guidelines by diabetes caregivers is needed to reduce the burden of diabetes complications.