Summary. Executive Function (EF) during childhood and early adolescence was considered in order to investigate: A) age effects on EF, B) main components of EF, C) relationship between different assessment tools. An Everyday Planning test and a Sentences Alternative Completion test were administered to 125 children from 3rd to 8th grade; their teachers completed a questionnaire about EF behaviors. Test results indicate that the major gain in planning ability is between 4th and 5th grade; at 3rd grade inhibition has already developed while there is a gradual improvement in flexibility and strategic behaviour from 3rd to 8th grade. Factor analysis on questionnaire scores reveals a three factor solution including: 1) Impulse control, 2) Metacognition, 3) Flexibility. An interesting pattern of correlation is found among performance-based tests and teacher's evaluation. The findings are discussed referring to current theories and previous experimental studies about the development of EF.