Based on a survey of inter-municipal unions (IMUs) and inter-municipal companies (IMComs) in Poland, this article identifies the most common motives for launching inter-municipal cooperation and the most frequently reported outcomes. The declared motives are compared with the perceived outcomes, with a particular focus on mismatch situations: disappointments (when the expected gain was not realised) and unexpected outcomes (when the reported outcomes exceeded initial expectations). The research shows that the latter are reported more frequently than the former. The most frequently indicated motives for cooperation were related to financial benefits and included cost reduction and applying for additional funding. The “defensive” motive of IMC – cooperation to maintain the status quo – is practically absent. The data also suggests that cooperation can be perceived as “a value in its own right”.