In our randomized trial on hyperbaric oxygen (HBO), it was shown that HBO could reduce dysphagia and xerostomia, which are frequently encountered after (chemo-) radiotherapy (RT) and/or surgery for head and neck cancer (HNC). A risk model and nomogram are developed to select those patients who most likely will respond to HBO treatment. A total of 434 HNC patients treated from 2000 to 2008 were analyzed and filled out the EORTC QLQC-30 and H&N35 questionnaires. Age, gender, chemotherapy, T and N stages, site, radiotherapy technique, RT boost, surgery of the primary tumor and neck, bilateral RT, and dose were analyzed in a statistical model. The discriminative value of the model was evaluated based on receiver operating characteristics (ROC), the area under the curve (AUC), sensitivity, specificity, and proportion of correctly classified measures. Significant factors in predicting swallowing problems are age, follow-up duration, tumor site, chemotherapy, surgery of the primary tumor and neck, and dose. For dry mouth, the significant factors are age, gender, tumor site, N stage, chemotherapy, and bilateral irradiation. For dysphagia and xerostomia, the area under the ROC curve is 0.7034 and 0.7224, respectively, with a specificity of 89/77%, sensitivity of 27/58%, and a positive predictive value of 83/67% for dysphagia and xerostomia, respectively. The developed predictive risk model could be used to select patients for costly hyperbaric oxygen treatment to prevent or reduce severe late side effects of HNC treatment. Our model serves as a guideline for the Department of Radiation Oncology to reduce costs by excluding patients not amenable to hyperbaric oxygen protocols. The nomogram presented is a useful tool for clinicians in assessing patient risks when deciding on follow-up strategies (e.g., hyperbaric oxygen treatment) after RT or surgery for HNC.