AbstractCross‐sectional relationships between free smooth surface and proximal caries were assessed in 3 age groups, comprising 252 subjects aged 12 yr, 301 aged 15–16 yr and 102 aged 18–19 yr. Caries diagnosis was clinically on while spot and radio graphically on enamel lesion level. Fair correlation between buccallingual and proximal caries observed among 12‐yr‐olds (r=0.47) declined in the older subjects (r=0.24). While statistically significant the variability in proximal caries, explained by buccal‐lingual lesions, was low (range 6–22%). Sensitivity and specificity for buccal‐lingual lesions as an indicator for proximal caries in the same tooth ranged from 0.37–0.44 and 0.84–0.91, respectively, with associated Pv+ and Pv– ranging from 0.41–0.44 and 0.84–0.91, respectively. Sensitivity and specificity for buccal‐lingual caries in identifying subjects with proximal caries ranged from 0.33–0.44 and 0.67–0.98, respectively. Pv+ ranged from 0.94–0.99 and Pv‐ from 0.06–0.35. ROC curve analysis yielded Az‐values of about 0.76 in the two younger age groups and 0.57 in the oldest. The results imply that information obtained from visual examination should be applied with caution when inferences about current caries status on proximal surfaces are made fro