Obesity-associated diabetes in adolescents is increasing throughout the world. In this study, body mass index and capillary blood glucose were measured in a randomly selected sample of adolescents from 3 Lebanese private schools. Obesity was evaluated according to International Obesity Task Force cut-offs. Out of 300 students, 18.7% were at risk of obesity and 3.0% were obese. Random glycaemia level was ≥ 140 mg/dL in 10.3% of students. In those fasting, 10.5% had glucose intolerance and 3.5% had diabetes. Glucose levels were significantly higher in overweight versus normal weight individuals 86 (SD 13) versus 96 (SD 16) mg/dL. Among the normal weight group 8.6% had abnormal glycaemia while among those who were overweight 37.0% had abnormal glycaemia. Lebanese school students have high rates of overweight and of obesity-associated diabetes and glucose intolerance.