OBJECTIVES: To enhance the quality of diabetes care in the Netherlands, so-called care groups with three to 250 general practitioners emerged to organise and coordinate diabetes care. This introduced a new quality management level in addition to the quality management of separate general practices. We hypothesised that this new level of quality management might be associated with the aggregate performance indicators on the patient level. Therefore, we aimed to explore the association between quality management at the care group level and its aggregate performance indicators. DESIGN: A cross-sectional study. SETTING: All Dutch care groups (n=97). PARTICIPANTS: 23 care groups provided aggregate register-based performance indicators of all their practices as well as data on quality management measured with a questionnaire filled out by 1 or 2 of their quality managers. PRIMARY OUTCOMES: The association between quality management, overall and in 6 domains ('organisation of care', 'multidisciplinary teamwork', 'patient centredness', 'performance management', 'quality improvement policy' and 'management strategies') on the one hand and 3 process indicators (the percentages of patients with at least 1 measurement of glycated haemoglobin, lipid profile and systolic blood pressure), and 3 intermediate outcome indicators (the percentages of patients with glycated haemoglobin below 53 mmol/mol (7%); low-density lipoprotein cholesterol below 2.5 mmol/L; and systolic blood pressure below 140 mm Hg) by weighted univariable linear regression. RESULTS: The domain 'management strategies' was significantly associated with the percentage of patients with a glycated haemoglobin <53 mmol/mol (beta 0.28 (0.09; 0.46) p=0.01) after correction for multiple testing. The other domains as well as overall quality management were not associated with aggregate process or outcome indicators. CONCLUSIONS: This first exploratory study on quality management showed weak or no associations between quality management of diabetes care groups and their performance. It remains uncertain whether this second layer on quality management adds to better quality of care