Aggression and social insecurity in children have received a lot of attention in recent research. In the current study the purpose was to examine whether specific demographic characteristics, such as gender, age (that is educational level and school class) and geographical area are significant factors for a child's aggressive and socially insecure behaviors. The sample was comprised of 652 preschool and elementary school students (194 and 458 children respectively; M age = 8.16 years, SD = 2.48) in Greece. Three hundred and twenty-three (323) of them were males and 329 were females. Results indicated that (a) boys tend to surpass girls in aggressive behavior, (b) children who attend higher elementary school classes tend to exhibit lower levels of aggression and social insecurity than those in kindergarten, and (c) children who live in urban areas are more aggressive and socially insecure than children in rural areas. The theoretical and practical implications of the present findings are discussed and recommendations are made for future research.