OBJECTIVE: To assess the risk factors for the presence and severity of obstructive sleep apnea (OSA) among obese patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: Unattended polysomnography was performed in 306 participants. RESULTS: Over 86% of participants had OSA with an apnea-hypopnea index (AHI) >or=5 events/h. The mean AHI was 20.5 +/- 16.8 events/h. A total of 30.5% of the participants had moderate OSA (15 <or= AHI <30), and 22.6% had severe OSA (AHI >or=30). Waist circumference (odds ratio 1.1; 95% CI 1.0-1.1; P = 0.03) was significantly related to the presence of OSA. Severe OSA was most likely in individuals with a higher BMI (odds ratio 1.1; 95% CI 1.0-1.2; P = 0.03). CONCLUSIONS: Physicians should be particularly cognizant of the likelihood of OSA in obese patients with type 2 diabetes, especially among individuals with higher waist circumference and BMI.