Patients with serious intellectual disability (ID) are occasionally unable to tolerate dental treatment when intravenous sedation or general anaesthesia (IVSGA) is involved. In order to make a decision regarding the application of IVSGA, the International Classification of Functioning, Disability and Health (ICF) is useful. Therefore, in this study, a set of codes involved in dental problems were chosen from the ICF, and patients with ID who could tolerate dental treatments were compared with those who could not. From preliminary interviews of six patients with ID, 16 codes were chosen, and an objective five-rank scale was then constructed for use with all chosen codes. Forty-nine ID patients who visited the Okayama University Hospital for dental treatment between January and April 2003 were evaluated. Facility workers were interviewed according to the code set chosen. The participants were then divided into two subgroups depending on their tolerability of dental treatment. The results of these groups for all 16 codes were then compared. Of the 49 patients interviewed, 23 were able to tolerate the dental treatment. In the Activities & Participation section of the ICF, the tolerable group showed lower disability levels with regard to d110 Watching, d540 Dressing and d550 Eating. In other sections, there were no significant differences between the groups. The code set chosen in this study and the five-rank scales in each code were useful as they enabled easy interviewing. The ICF was raised as a possibility for considering the application of IVSGA for dental treatment on patients with ID. For clinical use of the ICF, it is recommended that significant codes should be selected and that the five-rank scale is used so that more objective results are obtained from interviews.