Objectives: (1) To evaluate the effectiveness of adenotonsillectomy for the treatment of Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS) in children. (2) To evaluate the usefulness of respiratory polygraphy (RP) for controlling post-adenotonsillectomy effects. Methods: The children studied were referred to the Burgos Sleep Unit (SU) with clinical suspicion of OSAHS before undergoing adenotonsillectomy. For all patients, a clinical history was taken and a general physical examination, as well as a specific ear, nose, and throat examination was done. RP before adenotonsillectomy, and seven months afterwards, was also done. OSAHS was diagnosed if the Apnea Hypopnea Index (AHI) was >= 4.6. Results: Of the 100 children studied, 68 were male and 32 female, with an age of 4.17 +/- 2.05 years. Using RP, 86 of them were diagnosed with OSAHS before undergoing adenotonsillectomy. There was a significant improvement in all clinical and polygraphic variables after adenotonsillectomy. The pre and post surgery AHI index was 11.9 +/- 11.0 and 2.6 +/- 1.5, respectively, with a significant mean difference (9.4 +/- 10.9, p < 0.01). The residual OSAHS was 11.6% (CI 95%: 4.3-19%). Conclusions: Respiratory polygraphy is a useful tool for monitoring the effectiveness of surgical treatment and the detection of residual OSAHS in children with adenotonsillar hypertrophy. (C) 2012 Elsevier B.V. All rights reserved.