Research suggests that children with specific language impairment (SLI) have processing limitations; however, the mechanisms involved have not been well defined or investigated in a theory-guided manner. The theory of constructive operators was used as a framework to explore processes underlying limited processing capacity in children with SLI. Mental attentional capacity, mental attentional interruption, and 2 specific executive functions (shifting and updating) were examined in 45 children with SLI and 45 children with normally developing language, aged 7 to 12 years. The results revealed overall group differences in performance on measures of mental attention, interruption, and updating, but not shifting. The findings supported the premise that mental attention predicted language competence, but that this relationship was mediated partially by updating.