Studies examining the cognitive effects of a second language acquired in the context of linguistic immersion school program have led to contradictory results (e.g., Nicolay & Poncelet, 2013; Simonis et al., 2019). The main purpose of the present study was to determine if the attentional and executive skills of pupils attending a bilingual immersion program depend on the type of second language learned and the time spent in immersion classes. We assessed a range of attentional/executive abilities such as alerting, selective auditory attention, divided attention, cognitive flexibility and working memory in French-speaking 2nd and 5th graders attending immersion classes in English or Dutch since kindergarten as well as in control children attending ordinary classes. Arithmetic abilities were also assessed. In 2nd grade, the results showed no difference between English immersed, Dutch immersed and control groups for the attentional and executive tasks. However, for arithmetic tasks, the English immersed group performed worse than the two other groups. In fifth grade, the English and Dutch immersed groups outperformed the control group on the cognitive flexibility task. Furthermore, the Dutch immersed group outperformed the control group on the working memory task. Finally, the Dutch immersed group outperformed the English immersed and the control groups on arithmetic tasks. These results are discussed in terms of the length of time spent in linguistic immersion and the type of language learned.