Objective : Describe and analyze the variations in the relations between the attention capacity and the performance in reading activities, considering the age and the socioeconomic and cultural level in children of the first cycle of the primary school. Participants and Methods: 250 children, with ages between 6 and 9 years, students of primary , public and private schools, of the city of Mar del Plata, Argentina. Instruments: Scales of reading and attention of Batería de Evaluación Neuropsicológica Infantil -ENI- and Stroop Test. Results : The statistical analyses allow to confirm variations in the relations between the attention capacity and the performance in different reading activities (reading of words, pseudo words, orations, understanding and precision), based on the age and the socioeconomic and cultural level of subjects. Additionally, the results show evidences of significant differences of the attention capacity, depending on the used instruments to evaluate it. Conclusions : The results sustaining the idea of the attention capacity development and the narrow relations that maintains with the processes of reading learning, demonstrating the influences of means on both processes. Additionally the interaction between hereditary and environmental factors is discussed.