We investigated the outcome of uvulopalatopharyngoplasty (UPPP) combined with radiofrequency thermotherapy of the tongue base (RFTB) in patients with obstructive sleep apnea syndrome (OSAS) with both palatal and retroglossal obstruction, and we compared these results with the results of single level surgery (UPPP). A retrospective cohort study was performed in patients with mild to severe OSAS who underwent UPPP with or without RFTB. Seventy-five patients with both palatal and retroglossal obstruction underwent UPPP, 38 patients without RFTB (group 1) and 37 patients with RFTB (group 2). The outcome of the surgery was measured by both objective success (defined as a reduction of AHI >50% and AHI below 20) and subjective improvement. In group 1 the overall success rate was 42%, and in group 2 49%. Other polysomnographic values (AI, DI, mean SaO2) improved after surgery (not significant). No serious adverse events occurred. Surgical treatment of combined palatal and retroglossal obstruction remains a challenge. Adding RFTB to UPPP results in a mild improvement compared to UPPP alone. Although the addition of RFTB to UPPP seems to result in only a limited improvement, there is no major downside to it. RFTB is well tolerated and safe.