It is unclear whether patients with coronary artery disease (CAD) and diabetes mellitus (DM) can make comprehensive lifestyle changes that produce similar changes in coronary risk factors and quality of life compared with patients with CAD and without DM. We examined medical characteristics, lifestyle, and quality of life by diabetic status and gender in the Multicenter Lifestyle Demonstration Project (MLDP), a study of 440 nonsmoking patients with CAD (347 men, 55 with DM; 15.9%; 93 women, 36 with DM; 38.7%). Patients met in groups to improve lifestyle (plant-based, low-fat diet; exercise; stress management) for 1 year. Follow-ups were conducted at 3 and 12 months. At baseline, body mass and systolic blood pressure were significantly higher among patients with DM. Men with DM had a worse medical history (e.g., hypertension, hyperlipidemia, and family history of CAD) than did those without DM. Patients with DM, especially women, reported poorer quality of life than did patients without DM. The 2 groups of patients were able to adhere to the recommended lifestyle, as demonstrated by significant improvements in weight (mean -5 kg), body fat, low-density lipoprotein cholesterol, exercise capacity, and quality of life. No significant changes in triglycerides and high-density lipoprotein cholesterol were noted. By the end of 12 months, improvements in glucose-lowering medications (i.e., discontinuation or a change from insulin to oral hypoglycemic agents) were noted for 19.8% (n = 18) of patients with DM. In conclusion, patients with CAD and DM are able to follow a comprehensive lifestyle change program and show similar improvements in coronary risk factors and quality of life as those without DM.