Swedish Radiation Safety Authority has suggested guide-lines regarding information to individuals who undergo radiographic examinations. The guide-lines concerns medical care but patients in dental care can also be expected to have a wish to be informed about ionizing radiation. The main objective was to find out the patient’s perception of their knowledge about x-ray radiation and if they have a need to know more about x-rays. A questionnaire study was performed at two public dental clinics in Sweden during a twomonth period in the summer 2016. Patients ≥ 18 years old who gave their consent to participate were included in the study. Of all 429 participants 44 % declared an average knowledge about x-ray radiation and 37 % of all participants declared an inadequate knowledge. A total of 54 % had been informed about x-ray and its effects. School was the most common information source. Approximately 76 % had the perception that dental x-ray radiation is not harmful. 51 % declared the need to know more about x-ray. Approximately 52 % declared no knowledge about natural background radiation and 59 % declared it valuable to know more about dental x-ray in relation to natural background radiation. The participants showed mixed opinion and perception about x-ray radiation. A majority of patients want to know more about x-ray radiation. The study did not identify any particular group(s) needing more information about x-ray radiation than what is included in the justification of the radiographic examination.