Purpose: To assess the prevalence of developmental defects of the enamel (DDE) in permanent first molars and incisors and their association with dental caries in two age groups of children living in Wielkopolska, Poland. Materials and Methods: The sample consisted of 225 children ages 6-8 years and 245 children ages 12-14 years (mean age ± SD = 9.9 ± 2.6). Dental defects were described using the modified DDE index. Caries experience was recorded using the DMFT index (number of decayed, missing and filled teeth) for all permanent teeth and for first permanent molars and incisors (DMFT-IM). Results: Overall, 25.7% of the subjects had at least one permanent first molar or incisor affected by DDE. Diffuse opacity was the most common type of DDE, while hypoplasia was the least prevalent. The mean number of teeth with caries (DT) and the mean number of molars and incisors with caries (DT-IM) were higher in subjects with enamel hypoplasia and/or demarcated opacity than in subjects without DDE or with diffuse opacities (p 0.05). Caries prevalence was higher in children with hypoplasia and/or demarcated opacity than in subjects without DDE. The differences were statistically significant only for the younger group (p 0.05). Conclusion: The overall tooth prevalence of DDE in molars and incisors is comparable to that observed in low-fluoride communities. However, a preponderance of diffuse defects suggests the need for further investigation into the aetiology of DDE among Polish children. The results confirm that demarcated opacities and hypoplasia should be considered important caries risk factors. Keywords: demarcated opacity, dental caries, developmental enamel defects, diffuse opacity, enamel hypoplasia