PURPOSE: To verify the speech therapy aspects of the stomatognathic system, including phonoarticulatory structures (lips, tongue, and soft palate) and swallowing, respiratory, speech, and phonation (vocal quality and resonance) functions, before and after undergoing adenotonsillectomy. METHODS: The study included 22 children, 17 males and 5 females, aged between 5 and 10 years, suffering from hypertrophy of palatine and adenoid tonsils, with surgical indication for adenotonsillectomy and with no previous speech therapy. The speech-language pathology evaluation was performed before surgery and during the period between 1 and 6 months after adenotonsillectomy. It consisted of an evaluation of structures (lips, tongue, and soft palate) and of swallowing (liquid), respiration (mode), speech, and phonation (voice quality and resonance) functions. To evaluate vocal quality and resonance, 15 participants with the postoperative evaluation carried out in a period from 1 to 2 months were considered. RESULTS: There were differences regarding nasal respiratory mode, lips closed at rest posture, changed tongue tonus, adequate mobility of the soft palate, changed tongue posture during liquid swallowing, and absence of interposition compensatory mechanism of lips in swallowing. Reduction in the frequency of distortion processes was also found. With regard to speech, little improvement in vocal quality and resonance was seen. CONCLUSION: Following adenotonsillectomy, some structures and functions can spontaneously readapt or improve. However, most children needed to be referred to speech therapy for readapting stomatognathic structures and the assessed functions.