Background. The aim of the study was to analyze speech outcome for patients with advanced oral/oropharyngeal cancer treated with reconstructive surgery and adjuvant radiotherapy. Methods. Speech tests (communicative suitability, intelligibility, articulation, nasality, and consonant errors) were performed in a control group and in patients before treatment (n = 76), and 6 months (n = 51) and 12 months (n = 42) after treatment. Results. Speech tests were significantly worse for patients before and after treatment compared with the controls. Speech did not improve between 6 and 12 months. After treatment, patients with T3-4 tumors showed a significantly worse score for communicative suitability, intelligibility, and articulation than patients with T2 tumors. No significant differences were found for subsites after treatment, although patients with mobile tongue tumors showed the best results. Conclusion. Speech difficulties are significant, and with the knowledge of this study better counseling and vigilance as to speech difficulties may be possible in patients undergoing treatment for oral/oropharyngeal cancer.