BACKGROUND: Patients with type 2 diabetes are likely to have comorbid conditions which represent a high burden for patients and a challenge for primary care physicians. The aim of this cross-sectional survey was to assess the impact of additional comorbidities on quality of life within a large sample of patients with type 2 diabetes in primary care. METHODS: A cross-sectional survey within a large sample (3.546) of patients with type 2 diabetes in primary care was conducted. Quality of life (QoL) was assessed by means of the Medical Outcome Study Short Form (SF-36), self reported presence of comorbid conditions was assessed and groups with single comorbidities were selected. QoL subscales of these groups were compared to diabetes patients with no comorbidities. Group comparisons were made by ANCOVA adjusting for sociodemographic covariates and the presence of depressive disorder. RESULTS: Of 3546 questionnaires, 1532 were returned, thereof 1399 could be analysed. The mean number of comorbid conditions was 2.1. 235 patients declared to have only hypertension as comorbid condition, 97 patients declared to have osteoarthritis only. Patients suffering from diabetes and hypertension reached similar scores like diabetic patients with no comorbidities. Patients with diabetes and osteoarthritis reached remarkable lower scores in all subscales. Compared to patients with diabetes alone these differences were statistically significant in the subscales representing pain and physical impairment. CONCLUSION: The impact of osteoarthritis as an often disabling and painful condition on QoL in patients with type 2 diabetes is higher than the impact of hypertension as common but often asymptomatic comorbidity. Individual care of patients with chronic conditions should aim at both improving QoL and controlling risk factors for severe complications.