The aim of this study was to compare the retention and caries preventive efficacy of glass ionomer (Fuji III; GIC) and light-cured resin-based (Delton; LCR) fissure sealants. One hundred and sixty-six 5-14-year-old schoolchildren received sealants on their newly erupted first or second molars; a split mouth design was used. Previously reported 2-year results showed low retention rates for GIC sealants, but no difference in the caries increment between the groups. The same persons were invited to a dental check-up 6.1 to 7.8 (mean 7.1) years after the application of sealants; 111 persons (66.8% of the original group) participated in the study. The retention of sealants, and the caries status of occlusal surfaces and adjacent proximal surfaces was recorded. On the sealed occlusal surfaces, 10% of GIC and 45% of LCR sealants were totally and 9% of GIC and 20% of LCR sealants partially present. Twenty-three (23.5%) of the occlusal surfaces sealed with GIC and 16 (16.5%) of those sealed with LCR were carious or filled. Compared to LCR sealants, the effectiveness of GIC sealants was -44% (95% CI -71%, -16%) and net gain -7% (95% CI -18%, 4%). The relative risk of caries occurring was 1.44 (95% CI 0.96, 2.14).