The Swedish public bus transport sector is showing a negative development as costs are escalating and the number of passengers is stagnating. Based on theories in Public-Private Partnerships and inter-organizational cooperation, this paper presents an exploratory study how the cooperation between public and private actors affects the quality of public bus transport. Evidence shows that the negative development in the sector is mainly due to the nature of the contracts between public and private actors. Despite the contracts, two of four cases have increased their quality and public welfare through cooperation between the actors. The results highlight the importance of customizing the cooperation based on each actors ́ driving force in the contract. Additionally are detailed goal setting and a clear inter-organizational structure strongly correlating with increased quality, finally is trust identified as a corner stone for the construction of a successful cooperation.