OBJECTIVE: To examine the agreement between parents' and children's reports on four items of family affluence: number of cars, own bedroom, number of family holidays, and number of computers, and to analyse predictors of disagreement. DESIGN: Cross sectional child-parent validation study of selected items from an internationally standardised questionnaire. SETTING: Survey conducted in schools in Denmark, Germany, Hungary, Italy, Poland, and Scotland. PARTICIPANTS: 972 11-year-old children and their parents responded to the questionnaires. RESULTS: The child item response rates were high (above 93%). The percent agreement was low for holidays spent with family (52.5%), but high for the other three items of family affluence (76.2% - 88.1%). The kappa coefficients were good or excellent for all items (between 0.41 and 0.74) and the gamma coefficients were strong for all items (between 0.56 and 0.96). Children from single parent families were more likely to over-report family affluence (OR=2.67, CI: 1.83-3.89). CONCLUSIONS: Young adolescents' self-reports of family affluence are fairly valid across six countries. This finding suggests that the variables measured can be used in epidemiological studies which aim at ranking children according to socioeconomic position.