During recent decades there has been a rapidly growing interest in youths' sedentary behaviour and its association with cardio-metabolic health. Currently there is little-to-no evidence for a cross-sectional and longitudinal association between volume and pattern (bouts and breaks) of objectively measured sedentary behavior and body weight in youth. Likewise, there is little-to-no evidence for a cross-sectional association between volume and pattern of objectively measured sedentary behavior and other markers for cardio-metabolic risk in youth. However, there is sufficient evidence for a cross-sectional and longitudinal association between screen-time and body weight and blood pressure and blood lipids. Furthermore, there is evidence for a cross-sectional association between youths' screen-time and clustered metabolic risk and insulin resistance. Overall, the level of evidence was low and, therefore, caution is required when interpreting the results.