Abstract This study focuses on the clinical use of laser fluorescence compared to visual inspection (VI) for detecting and monitoring the progress of caries lesions during a one-year follow-up period and for screening subjects with unfavourable dietary habits causing demineralization of teeth. The effect of professional cleaning on laser fluorescence was also studied. The study groups were comprised of schoolchildren (n = 259), and altogether 3 651 occlusal tooth surfaces were examined visually and by using laser fluorescence. Laser fluorescence was found to be useful as an adjunct to visual inspection in detecting dental caries lesions during routine dental check-ups. The variation of laser fluorescence values in each visual category excludes its use as a primary or only method for caries detection. It rather functions as an alarm for a closer or more thorough examination. In addition, it can be a useful tool when deciding on the intervention method and the length of the recall-interval. The best cut-off point for considering operative intervention was found to be 30/99. Laser fluorescence was also found to be useful in monitoring lesion progression. Monitoring can be done through clear sealants. High laser fluorescence values (> 20) of sound tooth surfaces may predict decaying within a period of one year. Professional cleaning increased laser fluorescence values of molars, especially second molars. The increase was significant in molars with a visual score of > 0 or when visually detected initial and dentinal caries lesions were included. Professional cleaning was most efficient when using only a rubber cup and water spray without paste. A computer-based questionnaire on dietary habits was used to evaluate the cariogenity of children's dietary habits. The laser fluorescence values of tooth surfaces of children with harmful dietary habits were found to be higher than among children with favourable dietary habits. Laser fluorescence can be used for screening children whose current dietary habits may harm their teeth.