Purpose: To evaluate if using the laser fluorescence (LF) device improves the detection of early or more advanced occlusal caries lesions in primary teeth. Materials and Methods: A total of 181 occlusal sites in primary teeth were assessed by one examiner using DIAGNOdent. The same examiner and a second examiner evaluated 72 of the sites again to assess intra- and inter-examiner reproducibility. After histological validation, lesions were divided at three thresholds according to the lesion depth: outer half of the enamel (D1), inner half of the enamel (D2) and dentine (D3). The sensitivity, specificity, accuracy and area under ROC curve were calculated for cut-off points for the sample considering the aforementioned thresholds. The parameters were compared using chi-square test and by comparison between unpaired ROC curves. Results: The overall LF performance was better at dentine threshold than at enamel threshold. The higher specificity was found at D3 and D2, and higher accuracy at D3 (P 0.001). The intra- and inter-examiner agreements were classified as good or excellent for all thresholds. Conclusions: The LF device performs better at the dentine threshold than at the enamel threshold. This method does not perform well in detecting initial enamel caries lesions. Keywords: dental caries, early detection, laser fluorescence, occlusal surface, primary teeth