This study investigated cognitive-motor interference (CMI) and attentional resource management during development using a dual-task (DT) paradigm. Participants aged 7-9 years (n=11), 10-12 years (n=14), and adults (n=17) performed an auditory oddball task with two difficulty levels while sitting or walking on a treadmill. Cognitive and motor performance, along with P3a and P3b eventrelated potentials, were analyzed. Results showed improved cognitive and motor performance with age, associated with reorganization of brain responses. Children exhibited larger P3a and P3b amplitudes compared to adults, suggesting higher attentional resource allocation. Increasing cognitive difficulty led to decreased cognitive performance and increased P3a amplitude in children. Motor complexity resulted in decreased P3b amplitude in children, indicating reallocation of attentional resources to gait control. Notably, children aged 10-12 years demonstrated more adult-like CMI management strategies compared to younger children. The study revealed that attentional resource management evolves with age, with older children showing more efficient resource utilization despite similar resource allocation. These findings highlight the complex development of cognitive-motor systems and attentional resource management during childhood, emphasizing the importance of considering age-specific strategies in dual-task paradigms. The results contribute to understanding the developmental trajectory of CMI management and its implications for cognitive and motor performance in children.