OBJECTIVE To evaluate the reproducibility of quantitative light-induced fluorescence (QLF) for the detection and assessment of demineralization states of non-cavitated root surfaces and to determine the correlation between visual inspection and QLF-analysis. METHODS 46 exposed non-cavitated root surfaces of 12 participants were classified in three scores: sound (0), lesion ≤ 5 mm (1a), lesion > 5 mm in diameter (1b). Three examiners imaged every root surface three times using QLF (QRayCam) and measured fluorescence loss (ΔF) and lesion volume (ΔQ). The QLF-images were analyzed by three examiners. The intra- and interexaminer reproducibilities were calculated (intraclass correlation coefficient, ICC). The correlation between the scores of root caries and QLF-analysis was determined (rank correlation coefficient, Spearman-Rho ρ). RESULTS Intra- and interexaminer reproducibility (ICC) was 0.98 and 0.95 for ΔF, 0.94 and 0.91 for ΔQ, respectively. A significant correlation was observed between the scores and ΔF (ρ = -0.53, p < 0.01). CONCLUSIONS QLF as a reproducible diagnostic tool enables non-invasive detection and differentiation of non-cavitated root caries lesions on root surfaces in vivo. It can be recommended in addition to the clinical evaluation for prospective follow-up examinations of demineralization states of exposed root surfaces.