Aim: To investigate the long-term effects of adenoidectomy on dental and skeletal structures. Material and Methods: Twenty-six patients diagnosed with nasal obstruction were included in the study; adenoidectomy was recommended by an ear, nose, and throat specialist for all of the patients. Thirteen patients underwent adenoidectomy within the first year following diagnosis; these patients comprised the treatment group. The remaining 13 patients did not undergo adenoidectomy and comprised the control group. Lateral and posteroanterior cephalometric radiographs and study casts were obtained at the beginning of the study and 6 years later. Postoperative nasal resistance was recorded with a digital planimeter on lateral head cephalograms. The changes to the skeletal and dental structures were also recorded on lateral and posteroanterior cephalometric radiographs. Dental arch measurements were obtained on study casts. Results: Adenoidectomy had a minor effect on skeletal structures; the dental effect was more significant, particularly on maxillary and mandibular incisor inclinations. The maxillary and mandibular incisors were located anteriorly following the adenoidectomy (P < .05). In the treatment group, the interincisal angle decreased significantly (P < .01), nasal resistance decreased significantly, and the respiratory areas increased. Conclusion: Adenoidectomy alone may change only the breathing pattern, without having a significant effect on malocclusion and facial type. World J Orthod 2002;3:73–81.