The aim of the present study was to assess the level of self-perception, self-esteem, physical activity and sedentary behavior of primary school children between 10 and 12 years old in the city of Komotini (Rodopi East Greece, North), to investigate the correlation between the above parameters and to detect possible differentiation on each factor with regard to the age and gender of the children. The sample of the survey consisted of 153 students from five public primary schools. The students were divided according to their gender (boy-girl) and class grade. Data were obtained from the Self-Perception Profile for Children and the "Self-administered physical activity interview checklist". The analysis showed that self-perception, self-esteem and physical activity was on a satisfactory-high level. In addition, the sedentary behavior of participants was high. Physical activity had a positive effect on the self-concept/self-esteem. Girls were found to have a higher level of self-perception than boys in the behavior conduct scale, while boys generally showed higher global self -- worth compared to girls. Older students showed higher self-perception in scholastic and social competence, while they had a lower global self-worth. Moreover, it was noted that students whose parents had a high level of education had higher self-concept in scholastic competence.