OBJECTIVE: Given the rapid increase in the prevalence of childhood obesity, identifying the sociodemographic influences on obesity status is important for planning and implementing effective prevention initiatives. However, this type of data is limited for Greek children. Therefore the aim of the present study was to identify possible sociodemographic factors associated with childhood obesity at the national level. DESIGN: Cross-sectional, population-based survey, carried out from October to May 2009. Setting Under the context of the GRECO (Greek Childhood Obesity) study, a nationwide sample of 2315 primary-school children. SUBJECTS: Children aged 10-12 years and their parents were voluntarily enrolled. Direct anthropometric measurements of the children were obtained and information on sociodemographic characteristics of the parents, as well as their self-reported values of body weight and height, were collected. RESULTS: Overweight and obesity prevalence was 29·5 % and 13·1 %, respectively, among boys; 29·5 % and 9·0 %, respectively, among girls. Multiple logistic regression analysis revealed that the most important sociodemographic predictors of childhood obesity were mother's age, parental BMI classification and father's type of occupation. More specifically, increased mother's age and normal BMI status of the parents seemed to have a protective effect on the likelihood of having an overweight/obese child. Additionally, the odds of a female child of being overweight/obese were reduced when the father's type of occupation tended to be less manual. CONCLUSIONS: Anti-obesity health policy interventions have to address to the parents and promote their active involvement, to effectively confront the alarming magnitude of the paediatric obesity problem in Greece.