AIM: To describe the improvement in various aspects of quality of life (QoL) after coronary artery bypass grafting (CABG), in relation to a previous history of diabetes mellitus. PATIENTS: All patients from western Sweden who underwent CABG between 1988 and 1991 without simultaneous valve surgery. METHODS: Patients were approached with three questionnaires: The Physical Activity Score, the Nottingham Health Profile and the Psychological General Well-being Index prior to surgery and 3 months, 1 and 2 years thereafter. RESULTS: All three questionnaires already showed a significant improvement in QoL after 3 months, remaining at a similar level 1 and 2 years after the operation. In terms of Physical Activity Score improvement was of similar magnitude in diabetic and non-diabetic patients. In terms of the Psychological General Well-Being Index significant and similar improvements were found in diabetic and non-diabetic patients at each evaluation. In terms of the Nottingham Health Profile there was a significant improvement both in diabetic and non-diabetic patients 3 months, 1 and 2 years after the operation. However, improvement was more marked in diabetic than in non-diabetic patients at each evaluation. CONCLUSION: For 3 months, 1 and 2 years after CABG various aspects of QoL as estimated with three different instruments, improved significantly both in diabetic and in non-diabetic patients compared with the situation prior to the operation. However, the three instruments differed somewhat. Thus, whereas in the Physical Activity Score, diabetic patients tended to improve less markedly than non-diabetic patients, the opposite was found in the Nottingham Health Profile.