We study the role of relative childhood and adolescent obesity in the development of noncognitive abilities. We employ a novel identification strategy, utilizing the fact that one's body size is a relative concept and there are large variations in body sizes across MSAs. We focus on children who move between MSAs. Controlling for origin-destination state pair fixed effects, we find that a 10 percentile point increase in relative body size would increase behavioral problems by 2 percentile points. This effect is of a similar magnitude to a two-year reduction in maternal education.