140 Abstract Background Head and neck cancer (HNC) and its treatment often negatively impact swallowing function. The aim was to investigate the course of patient reported swallowing problems from diagnosis to 3, 6, 12, and 24 months after treatment, in relation to demographic, clinical and lifestyle factors. Methods Data were used of the Netherlands Quality of Life and Biomedical Cohort Study in head and neck cancer research (NET-QUBIC). The primary outcome measures were the subscales of the Swallowing Quality of Life Questionnaire (SWAL-QOL). Linear mixed-effects models (LMM) were conducted to investigate changes over time and associations with patient-, clinical-, and lifestyle parameters as assessed at baseline. Results Data were available of 603 patients. There was a significant change over time on all subscales. Before treatment, 53% of patients reported swallowing problems, and 70%, 59%, 50% and 48% at 3, 6, 12, and 24 months after treatment, respectively. Swallowing problems (i.e. longer eating duration) were more pronounced in case of female, current smoking, weight loss prior to treatment, stage III or IV tumor, and were more prevalent at 3 to 6 months after treatment. Especially patients with an oropharynx and oral cavity tumor, and patients receiving (C)RT following surgery or CRT only showed a longer eating duration after treatment, which did not return to baseline levels. Conclusion Half of the patients with HNC report swallowing problems before treatment. Eating duration was associated with sex, smoking, weight loss, tumor site and stage, treatment modality, and was more pronounced 3 to 6 months after treatment.