The goal of this work and research was to determine age differences in the nutritional status of preschool children. The task of this final paper was also to observe and clarify the differences between normal body weight, overweight, obesity and malnutrition. For the proper growth and development of the child, it is important to allow the child daily physical activity, being outdoors, as well as proper nutrition. Also raise awareness of the current situation, where research has shown that every third child is overweight. In order for the research itself to be possible, data on body height (HW) and body weight (WW) of children were needed. Using these values, we calculate the body mass index (BMI), and then determine the body mass index in percentiles. The research was conducted in the "Didi" kindergarten, which is located in the vicinity of Zagreb. The research was conducted on a sample of 22 children, of which 12 were 5 years old and 10 were 6 years old. The results proved that the majority of respondents were of normal nutrition, but that is why the number of obese children is significantly higher than the number of overnourished and undernourished children. It is important to raise awareness on this topic and to conduct more research for the progress of educational institutions and the proper growth and development of children.