Introduction: Obesity is defined as the excess of adipose tissue in the body, which is the result of genetic and behavioural factors, which cause chronic positive energy balance. In addition to genetic factors, there are also other factors that influence on the emergence of obesity, such as gender, ethnicity, inappropriate energy intake, and increase in sedentary lifestyle and decrease in physical activity. Obesity effects on the emergence of cardiovascular diseases, diabetes, cancer and musculoskeletal abnormalities, such as osteoarthritis. The prevalence of obesity and overweight among adults is 39% and 18% among children and adolescents. In the past few years, obesity has become a major public health problem. Children and adolescents with obesity have a higher chance to be obese in adulthood, which can lead to different chronic diseases. Purpose: The purpose of this diploma was to determine the effects of aerobic exercise on body mass index, body fat percentage, waist and hips circumference and cardiorespiratory fitness in children and adolescents with obesity or overweight. Methods: Literature was gathered in the database Pubmed. Articles were searched with the following keywords: childhood obesity, exercise, aerobic exercise and physical therapy. We included seven randomized controlled trials in English, which corresponded the inclusion criteria. Results: The examined researches have shown that aerobic exercise can statistically significant (p<0.05) improve body mass index, body fat percentage, waist circumference and cardiorespiratory fitness in children and adolescents with overweight and obesity. Discussion and conclusion: Further researches should have a better control over energy intake, a more structured progress to achieve the amount of exercise that is recommended. Despite the few limitations that the researches had, the results have shown that aerobic exercise has a positive impact on body composition, cardiorespiratory fitness and cardiovascular risk factors.