This study aims to analyse the effects of the decentralization level of collective wage bargaining on the wage level and the wage dispersion in Belgium. For this purpose, we have constructed a composite indicator of collective bargaining decentralization, based on variables that determine collective bargaining. Our results indicate the presence of a significant wage bonus and wider wage disparity in industries where collective bargaining is decentralized. Furthermore, we compare these results with those that use as an indicator of bargaining decentralization, the presence of collective agreements at company level, a commonly used indicator in the literature. We notice that this latter indicator seems to underestimate the degree of bargaining decentralization and thus also its effects on the wage structure. One can explains this result by the fact that in Belgium, besides firm collective agreements, the bargaining system also provides mechanisms that enable firms to distance themselves from collective agreements set at industry level.