Introduction. A systematic increase in the frequency of excessive body mass in young Poles is an argument supporting the need for identification persons with the increased risk. It is justified to test the level of comparability of the applied screening methods and criteria of diagnosing excessive body mass and body fat in the adolescent group.Aim. To assess the comparability of the results in terms of frequency of diagnosing of overweight and body fat excessive content depending on the method and assessment criteria in 18-year-olds.Material and methods. The study comprised 141 secondary school students (100 women and 41 men), with the age median of 17.8 ± 0.5 years. The measurements included height and body mass (to calculate the BMI) and assessment of the percentage of body fat content with two methods of bioelectric impedance in two bipolar versions: Tanita BC-570 and Omron BF-306.Results. Excessive body mass, as defined by the BMI, was found in 12.1% of students. The incidence of diagnosing excessive contents of body fat in the organism depended on the method of measurement and criteria of results interpretation; 20.6% with the Tanita and 28.3% with the Omron method. The measurements with Tanita BC-570 scales demonstrated stronger correlation with BMI value (p<0.001; r2=0.34) than measurements with the Omron BF-306 (p<0.001; r2=0.16).Conclusions. In young adults: 1. the diagnosis of excessive body mass by BMI and measurement with use of the bioelectric impedance methods with two bipolar versions (Tanita BC-570, Omron BF-306) provided inconsistent results. 2. The proportion of young people with excessive body fat was greater than indicated by the BMI norms. 3. The measurement with Tanita BC-570 scales demonstrated stronger correlation with BMI values than by the ones with the Omron. 4. Critical approach to the applied methods is indispensable in screening studies of nutrition level among adolescents.