PurposePredictors for the outcome of uvulopalatopharyngoplasty with and without tonsillectomy (UPPP ± TE) in sleep-disordered breathing have not been fully established. This study investigates tonsil grade, volume, and preoperative examination in predicting radiofrequency UPP ± TE outcomes.MethodsAll patients undergoing radiofrequency UPP with tonsillectomy if tonsils were present between 2015 and 2021 were retrospectively analyzed. Patients underwent a standardized clinical examination, including Brodsky palatine tonsil grade from 0 to 4. Preoperatively and 3 months after surgery, sleep apnea testing was performed using respiratory polygraphy. Questionnaires were administered assessing daytime sleepiness using the Epworth Sleepiness Scale (ESS) and snoring intensity on a visual analog scale. Tonsil volume was measured intraoperatively using water displacement.ResultsThe baseline characteristics of 307 patients and the follow-up data of 228 patients were analyzed. Tonsil volume increased by 2.5 ml (95% CI 2.1–2.9 ml;P< 0.001) per tonsil grade. Higher tonsil volumes were measured in men, younger patients, and patients with higher body mass indices. The preoperative apnea–hypopnea index (AHI) and AHI reduction strongly correlated with tonsil volume and grade, whereas postoperative AHI did not. The responder rate increased from 14% to 83% from tonsil grade 0 to 4 (P< 0.01). ESS and snoring were significantly reduced after surgery (P< 0.01), but the reduction was not influenced by tonsil grade or volume. No other preoperative factor other than tonsil size could predict surgical outcomes.ConclusionsTonsil grade and intraoperatively measured volume correlate well and predict the reduction of AHI, while they are not predictive of ESS and snoring response after radiofrequency UPP ± TE.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00405-023-07914-0.