The study aimed to show the changes on artrokinematic parameters of the neck and swallowing function after radiotherapy (RT) in head and neck cancer (HNC) patients. The fourty patients with HNC have been evaluated before, 1 and 3 months after RT. The posture, normal joint movement, muscle strength and endurance of the neck were evaluated as artrokinematic parameters. The clinical and radiological swallowing function evaluations were also done. Mean age of patients were 53,22±10,92 years. Head anterior tilt, kyphosis and shoulder protraction were more in the 3rd month after RT in posture analysis (p< 0.001). The neck flexion, lateral flexion and rotation limitations have increased (p< 0.001), neck muscle strength and endurance have gradually decreased (p< 0,001) after RT. At the same time, swallowing phases have been adversely affected after RT with all these side effects (p< 0.001) and the severity of aspiration in all consistencies has increased gradually (p< 0.05). As a result, RT starts to show its negative effects from the early period of cancer treatment. Unlike other studies, we concluded that RT affects head and neck structures negatively and these describes how RT affects swallowing function. So it is highly important to include head and neck structure mobility, strength and endurance assessments and exercises in swallowing rehabilitation.