The article deals with the issues of transformation of ownership of the banking system in Ukraine and Poland. Poland’s experience of successful privatization of the state banks has also been discussed. The place of the state banks preparing for privatization in the banking system of Ukraine has been analysed. By using the method of calculating the concentration of capital by the indicators of the share of the entity in the market (Pj), concentration ratio CRn and the Herfindahl-Hirschman Index (HHI), it has been found that the concentration level of the banking system in Ukraine in recent years is growing. Given the unstable situation, we can assume that the increased concentration within the normal range is a form of consolidation. However, given the current problem of hidden monopolies in Ukraine today, the transformation of ownership in the banking sector needs special attention of banking regulators to assess the possible socio-economic consequences of concentration.