Bridges face increasing demands due to higher traffic loads and more load cycles, which might require strengthening actions. In the Nordic countries, many existing steel girder bridges have non- composite concrete decks. A rational strengthening approach is to install shear connectors, enabling composite action between the deck and the girders for a more efficient use of the structural components. Installing shear connectors in a new steel structure is inexpensive but installing them in existing bridges can be costly. Instead of placing connectors along the entire bridge, they can be strategically installed where they give the most impact, using only as many as needed to get an adequate composite action. Case studies show that selective placement of shear connectors can significantly improve load-bearing capacity while reducing installation efforts. This paper describes two case studies, one single span bridge and one continuous steel-concrete bridge, where the impact from the position of the shear connectors has been evaluated.