© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Objectives (i) To quantify the importance that dentists place on caries risk factors when developing a caries treatment plan and (ii) to test the hypothesis that the ratings of importance for specific factors are significantly associated with whether or not the dentist performs caries risk assessment (CRA). Methods This study used a cross-sectional study design consisting of a questionnaire survey. The study queried dentists who worked in outpatient dental practices who were affiliated with the Dental Practice-Based Research Network Japan (JDPBRN), which seeks to engage dentists in investigating research questions and sharing experiences and expertise (n = 282). Participants (n = 189) were asked to rate the importance of caries risk factors when developing a caries treatment plan in both adult and pediatric patients. Results Oral hygiene status was rated as the most important risk factor when developing a treatment plan in both adult and pediatric patients, whereas the use of fluorides was rated as the least important. Results of multiple logistic regression analysis showed that the odds ratios for the decision to perform CRA in the adult patient for past caries experience and use of fluorides were 2.61 (95% confidence interval [CI]: 1.29-5.29) and 1.85 (95% CI: 1.12-3.04), respectively, whereas that for oral hygiene was 3.84 (95% CI: 1.15-12.79) and use of fluorides 1.79 (95% CI: 1.06-3.03) in the pediatric patient. Conclusions These results suggest that enhancing dentists' concept of the importance of current use of fluorides when developing a treatment plan may increase the percentage of dentists who conduct CRA in both adult and pediatric patients (clinicaltrials.gov registration number: NCT01680848).