The aim of the present study was to investigate cancer patients’ experiences of oral hygiene information, oral care and self-care, information on oral complications, examination of the oral cavity, and ability to eat and drink during cancer treatment, and to explore patient attitudes to oral examination and oral hygiene. The sample consisted of 41 consecutive patients treated with radiotherapy for head and neck cancer (n = 18) or with chemotherapy for haematological malignancies (n = 23). Patients were interviewed at the end of radiotherapy or the second/third chemotherapy cycle. Compared with patients receiving chemotherapy, those who received radiotherapy had significantly more often visited hospital dentistry, been informed about oral complications and oral hygiene, received instructions in oral hygiene procedures, and been examined by hospital staff. More of the radiotherapy patients experienced oral symptoms and difficulties to eat and drink during treatment. There were no significant differences between the groups with regard to patient experiences of the oral hygiene procedures. Only one patient objected to having hospital staff discuss oral hygiene procedures, and three did not want hospital staff to examine their oral cavity. Patients undergoing radiotherapy or chemotherapy need to be monitored during treatment with regard to their oral status and oral symptoms and complications. There are no acceptable reasons for allowing patients to suffer from oral symptoms that can be reduced.