Summary Aims:  To assess the evolution of type 2 diabetes mellitus (T2DM) quality indicators in primary care centers (PCC) as part of the Group for the Study of Diabetes in Primary Care (GEDAPS) Continuous Quality Improvement (GCQI) programme in Catalonia. Methods:  Sequential cross‐sectional studies were performed during 1993–2007. Process and outcome indicators in random samples of patients from each centre were collected. The results of each evaluation were returned to each centre to encourage the implementation of correcting interventions. Sixty‐four different educational activities were performed during the study period with the participation of 2041 professionals. Results:  Clinical records of 23,501 patients were evaluated. A significant improvement was observed in the determination of some annual process indicators: HbA1c (51.7% vs. 88.9%); total cholesterol (75.9% vs. 90.9%); albuminuria screening (33.9% vs. 59.4%) and foot examination (48.9% vs. 64.2%). The intermediate outcome indicators also showed significant improvements: glycemic control HbA1c ≤ 7% (< 57 mmol/mol); (41.5% vs. 64.2%); total cholesterol ≤ 200 mg/dl (5.17 mmol/l); (25.5% vs. 65.6%); blood pressure ≤ 140/90 mmHg; (45.4% vs. 66.1%). In addition, a significant improvement in some final outcome indicators such as prevalence of foot ulcers (7.6% vs. 2.6%); amputations (1.9% vs. 0.6%) and retinopathy (18.8% vs. 8.6%) was observed. Conclusions:  Although those changes should not be strictly attributed to the GCQI programme, significant improvements in some process indicators, parameters of control and complications were observed in a network of primary care centres in Catalonia.