Nowadays, there is still debate about the origin of arithmetic disabilities. Two predominant hypotheses have been developed in this regard: 1) difficulties in arithmetic appear due to a deficit in domain-specific skills (numerical skills) and 2) there is a strong relationship between the development of the domain-general processes and arithmetical skills. In this study we explore the specific contribution of orienting and executive control attentional networks to individual variability in basic mental arithmetic. Participants were elementary school children, from second to third grade, with and without difficulties in basic mental arithmetic. Results provide support for the two proposed hypotheses. Children with difficulties in arithmetic showed difficulties both in numerical skills and in attentional networks. These findings suggest that arithmetic difficulties may be associated with a heterogeneous combination of deficits, including difficulties in attentional functioning.