The objective of the questionnaire survey was to evaluate some selected elements of nutritional behaviours of 1015 secondary school children in Warsaw. The substantial number of the polled could not judge whether or not they ate properly and in accordance with the principles of well-balanced diet or they found their dietary habits to be improper. The secondary school children usually ate 3 – 4 meals a day; the girls cut down, significantly more often than the boys, on the number of their meals per day. A lot of improper dietary habits were found among the secondary school children. More than 80 % of all the respondents ate snacks between main meals. Vegetables were eaten mainly as an addition to lunch/dinner, and only a few children (about 10 %) had vegetables for their afternoon snack and dinner. Many secondary school children did not have their first and second breakfast at all, or they had just bars (of chocolate) for their second breakfast. The secondary schools contribute significantly to forming proper nutritional behaviours of their students, and ca. 30 % of the secondary school children declared to have acquired their knowledge of rational nutrition at school. The results of this questionnaire survey prove that it is indispensable to carry out nutrition education among school children and their parents in order to develop proper diet habits and to rectify mistakes made in this field.