Introduction. Epidemiologic investigations prove the increasing frequency of overweight occurrence in Poland as well as all over the world. Obesity epidemic results from environmental conditionings: availability of highly processed and cheap food which is full of fats and carbohydrates and shortage of physical activity. The main indicator of health is an appropriate lifestyle and that is why an effective health education among adolescent people is crucial. The important element of healthcare for children and teenagers is to show them the ability of making sound choices which should result in societies’ better health condition. The aim of this project was to estimate high school learners’ knowledge of obesity effects and its prevention. Materials and methods. The research has been conducted in secondary schools in Nowy Targ and Krościenko from November 2007 to March 2008. The research tool was a diagnostic opinion poll and a survey. There were 659 interviewees aged 16–19; 266 male (40,3% of surveyed) and 393 girls (59,7%). The results. The effectiveness of health education concerning excess weight prevention among the students of high schools is unsatisfactory. Conclusions. Planning health education among young people one has to take into consideration boys who are of lower level of knowledge especially and to include particular unknown pieces of information. In order to increase the efficiency, health education should be tightly connected with the prevention and health promotion program. Moreover it should be realized in cooperation with school workers and the parents.