Abstract. Child and adolescent obesity currently affects at least 10-25% of the paediatric population in most developed countries. The BMI value is one of the most appropriate method of defining obesity and has a strong association with body fatness and health risk. Two main environmental factors, nutrition and physical activity, could influence paediatric obesity development. This paper studies the relationship between sedentariness, snack and soft drink intake and overweight or obesity in children. 1194 primary school children (age 8-10) participated in the study. For all the subjects we measured the anthropometric data to calculate the BMI. The overweight and obesity prevalence was estimated using age-specific BMI cutoffs. A questionaire was also submitted to all the children by a single interviewer to obtain data about: a) Weekly Physical Activity, b) Weekly Sedentary Activity, c) Alimentary Style. Spearman rank correlation and the Student's t-test were used. The data demonstrated that 23.2% of the children is overweight and the 4.8% obese. BMI is inversely correlated to the physical activity, while there is positive correlation between BMI and number of double portions. Statistically significant positive correlation is present among eating snacks and hours of sedentariness, while there is a negative correlation between physical activity and TV hours. Physical activity in the childhood could be an important tool to prevent obesity development and adult-onset chronic diseases. It is important to encourage an active lifestyle in order to reduce sedentariness.(Biol.Sport 26:349-367, 2009)