With around 351. 8 billion Euro the cohesion policy accounts for almost one third of the European Union’s budget in the period 2014–2020. Numerous programmes and projects are co-funded by the so-called European Structural and Investment Funds (ESIF). Errors in public procurement cause almost half of all irregularities detected in these programmes and projects. Many of these errors could be avoided if ESIF-programmes would not foresee such strict rules for purchases and the intensity and frequency of controls of programmes and projects would be reduced to an adequate level. Based on five hypotheses the present article illustrates difficulties and helpful approaches for the challenging balancing act between ESIF- and EU-procurement rules.