Over the last couple of decades, several studies have found a link between bilingualism and improved performance on tasks measuring the core executive functions inhibition, shifting, and updating. However, results are inconsistent, and the existence of this proposed bilingual advantage is highly debated. This thesis investigates the hypothesis that bilingualism could be one of the contributors to the enhancement of executive functions (EF). The primary focus is the exploration of bilingualism as a continuum over two axes: use and proficiency, and further, to test whether L2 use is a better predictor of EF abilities than L2 proficiency. The data for this study comes from 82 Norwegian academics of similar age and socio-economic status, but who are differing in degree of bilingualism. Correlation and linear regression models were used to compare their performance on tasks measuring shifting (the trail-making task and the plus-minus task) and inhibition (two Stroop tasks and a Flanker task), as well as two measures for monitoring abilities (the sequential congruency effect score and overall reaction times on the Flanker task). The results of the analyses provide no further evidence for the existence of a bilingual advantage, possibly due to a ceiling effect. The results are further discussed in light of problems with EF measurement, and the question of whether certain patterns of L2 use are more likely to influence cognitive abilities than others.