A longitudinal study addressed the effect of COMT gene Val158Met polymorphism on memory narratives of children. The effects of sex and maternal education were also studied. The total sample consisted of 486 children (48.9% boys), who were 4 years old during the first and 6 six years old during the second wave. COMT gene Val158Met polymorphism had an effect on the number of memory details in autobiographical memories with Met/Met homozygotes providing more details than the children with the Val/Met genotype. A genotype by maternal education interaction was observed at the age of four, but not at the age of six: Met/Met genotype children in the lower maternal educational attainment group had more detailed memories at the age of four than their Val/Met counterparts.