Objective: To test the effect of a long-term weight loss rehabilitation program in extremely obese adolescents on breathing parameters during sleep. Methods: Thirty-eight extremely obese [mean body mass index (BMI) 45.3 +/- 7.9kg/m(2)] adolescents participated during a three- to nine-month period in an inpatient weight loss rehabilitation in a specialized long-term rehabilitation center. Breathing parameters were registered via a seven-channel portable screening device. Body weight and arterial blood pressure were measured before and after the long-term treatment. Results: Mean BMI decreased from 45.3 to 35.8 (p < 0.001), mean diastolic blood pressure decreased from 89 mmHg to 81 mmHg (p = 0,002). Nine patients had a RDI of >/=5 and 30 patients a RDI of <5; the mean RDI decreased from 4.08 to 3.27 (n.s.). Within the group, the RDI was >/=5 and the mean RDI decreased from 10.3/h to 5.2/h (p = 0.02). The mean SaO2 increased from 93.65 to 95.35% (p = 0.003), lowest SaO2 increased from 72.14 to 73.19% (n.s.) and snoring frequency decreased from 37.56% of total sleep time (TST) to 32.86% of TST (n.s.). Conclusion: A long-term inpatient weight loss program has a positive effect on breathing parameters during sleep in extremely obese adolescents. However, the effect on apneic events and snoring is relatively minor compared to the effect on arterial oxygen saturation. The role of obesity in the origin of respiratory events and snoring in adolescents might be overestimated.