OBJECTIVE The aim of this clinical caries detection study was to compare the outcome of quantitative light-induced fluorescence (QLF) and meticulous visual inspection (VI) in detecting non-cavitated caries lesions on occlusal surfaces in young adolescents. It was hypothesized that the respective diagnostic performances of meticulous VI and QLF are similar. METHODS The subjects were 34 fifteen-year-old students. Five-hundred-and-seventeen cleaned occlusal surfaces were air-dried and examined using VI. Fluorescence images were captured with QLF equipment and custom software was used to display, store and analyze the images. The area of the lesion (area; mm2), fluorescence loss (DeltaF;%) and DeltaQ (Area*DeltaF; mm2*%) were determined at a QLF threshold of -5%. The presence/absence of non-cavitated lesions was independently recorded with both methods. RESULTS 78.8% of all untreated surfaces were classified as sound or as having a non-cavitated lesion with both methods uniformly (VI+QLF). On 7.1% of all surfaces a lesion was detected by VI only and on 14.1% by QLF only. All parameters (Area, DeltaF, DeltaQ) differed significantly between lesions registered with both methods (VI+QLF) and lesions recorded with QLF only. CONCLUSIONS It was concluded that our hypothesis cannot be confirmed. The study shows that QLF detects (1) more non-cavitated occlusal lesions and (2) smaller lesions compared to VI. However, taking into consideration time-consuming image capturing and analysis, QLF is not really practical for use in the dental office.