Objective: Childhood obesity is on the rise globally, and family environment and socio-economic factors can play a relevant role. In Italy, regional differences in the prevalence of childhood obesity are observed. This study aimed to investigate the interaction between geographical region of residence, family environment and obesity among Italian adolescents. Design and method: Students of primary or secondary schools and their parents, residing in Calabria (South Italy) and Tuscany (Central Italy), were enrolled in a cross-sectional study. All participants were asked to fulfill a questionnaire composed of four sections. First section investigated demography and anthropometry, while General and Sport Nutrition Knowledge questionnaire (GeSNK), Mediterranean Diet Score, and International Physical Activity Questionnaire (IPAQ) assessed nutritional knowledge, dietary habits and physical activity levels respectively. BMI was calculated and students were classified using WHO BMI-for-age charts. Determinants of students’ habits and BMI were investigated with multivariate regression analyses. Results: 179 students and 113 parents from Tuscany, 247 students and 185 parents from Calabria participated in the study. Obesity prevalence was higher in Calabria than in Tuscany among both students and parents, however multivariate regression analysis showed that geographical region of residence was not in itself a determinant of the BMI of students. Although transmission of eating and physical activity habits from parents to sons appears to occur, parental BMI was the only parental characteristic identified as an independent determinant of the students’ BMI at multivariate regression analysis (adjusted for geographical area, students’ age and gender, parental BMI and education level, parents’ and students’ habits and nutritional knowledge). Conclusions: Prevention strategies oriented to reduce childhood obesity should also involve parents.