Previous studies of head and neck cancer patients going through radiation treatment have shown the treatment causes great physical as well as psychosocial problems. Although previous research acknowledges the needs of cancer patients, there is a lack of literature regarding the patient's perspective about radiation therapy. Studies have rarely focused on the whole experience of radiation treatment. The aim of this study was to illuminate how head and neck cancer patients' encounters with radiation therapists influence patients' experiences going through radiation therapy. The study was conducted via qualitative interviews, using a phenomenological hermeneutic approach. Eleven cancer patients were treated with radiation therapy. This study showed that encounters with radiation therapists have a significant influence on patients' experiences. Cancer patients' contact with radiation therapists can lead to increases or decreases in existential anxiety. When patients experience that the radiation therapist is professionally competent, the existential anxiety decreases. When the radiation therapist make time to build relationships and take responsibility for treatment and side effects, this creates a feeling of security and the treatment is easier to review. The study may indicate that the patients' existential anxiety increases when the radiation therapist shows professional incompetence.