Background It is important for dentists and hygienists to evaluate the oral health-related quality of life (OHRQoL) of patients, in order to depict with accuracy the burden of the disease on them, and thus to reach their specific needs. In a previous study, we observed that caregivers tended to overestimate the burden of dental conditions on patients’ life. Aim of the study In the present study, we further analysed those data using multilevel analysis, to investigate the possible determinants of the low concordance between patients’ and caregivers’ evaluation of OHRQoL, taking into account the role of the different caregivers and clinics. Methods This study consisted of a simultaneous assessment of patients’ oral quality of life, performed both by patients themselves and by their caregivers. Data were collected in four clinics, and patients were evaluated by 27 caregivers (15 dentists and 12 hygienists). OHRQoL was measured using the OHIP-14, that contains measures of physical, psychological and social abilities, general physical function, ability of speech and eating, symptoms of pain and discomfort, and appearance and social embarrassment. We tested eight multilevel models, using the OHIP difference as the dependent variable. In each model, the variance for the fixed effect (i.e., the levels) and the random effects (i.e., the intercept and other variables) was estimated. Results Data were complete for 432 patients. The mean difference between the caregivers’ OHIP and the patients’ OHIP was 4.4 (SD=8.2). The variance due to patients was partly explained by their age (higher OHIP difference in elderly vs young patients), gender (higher OHIP difference in women vs men), and number of teeth (higher OHIP difference in patients with less teeth). Almost 30% of variance was due to caregivers, while the effect of clinics was not significant. Conclusions The differences in caregivers’ evaluation could depend on the different caregivers’ experience, or their personal ability to empathize with the patient, or at least in part descend from different conceptual models of dental disease among caregivers. It is important to study the possible causes of the different judgments concerning patients’ OHRQoL by patients and caregivers, in order to improve the patients’ satisfaction of care, and to help patients to reach a well-informed decision about the treatment. Acknowledgement. The study was supported by the Swedish Research Council. DA is supported, in part, by funds from the "Progetto Ricerca Corrente" of the Italian Ministry of Health, Rome, Italy.