Obesity is considered to be one of the diseases related to the change in the lifestyle, leading to increased incidence of myocardial infarction, type 2 diabetes mellitus, hypertension and other diseases. Due to the progressively increasing prevalence of obesity in adulthood, prevention of obesity has to start in childhood and adolescent, in which also increase in prevalence of obesity was found. Actual prevalence of overweight and obesity was tested in this thesis by different standards (5. NAS, WHO, IOTF, CDC) in Czech children population in age of 6.5 - 7.5 years in 2013. Its trend since 1951 was evaluated. Since 2008 maintaining of the values in all categories at the constant level was found. The role of risk factors assessed by personal, family and school questionnaires in overweight prevalence was tested. The most important factors were diet, exercise and family factors. Increased weight/height ratio (WHtR) marker of adipose tissue was found in the category of normal weight children also and it shows the link with above-mentioned risk factors of diet, exercise and family prediction. Key words Obesity, Overweight, Prevalence, Childhood, BMI, 5. NAS, WHO, IOTF, CDC, COSI, WHtR, Waist circumference, Risk factors