In Germany and Switzerland, the realisation of large-scale projects is always the subject of controversial discussions. The media often give the impression that there is a lot wrong in Germany and that everything is fine in Switzerland. It is therefore investigated whether such an assessment for large underground construction projects is justified according to scientific criteria. For this purpose, a measurement system was developed to evaluate the success of large underground construction projects based on seven success criteria. This system was applied to 70 large underground construction projects in Germany and Switzerland. In addition to a quantitative comparison of the two countries, this article highlights differences with regard to the individual success criteria. The results show that large underground construction projects in Switzerland are not conclusively more successful than in Germany. However, the decisive factor for the respective project success is the quality of cooperation among the project participants.