Given the scale of infrastructure investment required over the coming decades, Eastern Partner (EaP) countries, like most countries around the world, are seeking to mobilise more private finance for infrastructure development. Strengthening the role of the private sector in infrastructure offers an opportunity to scale up investment in quality infrastructure and help realise efficiency gains in their operation, but it is difficult to achieve. The complex nature of public-private interaction requires considerable attention from policy makers for defining the modalities of private involvement, reflecting the long-term costs in the budgetary process and adequately sharing the associated risks between the public and private co-contractors.