The paper presents the methodological approaches to the definition of shadow economy in the world and different estimates of the shadow economy in Ukraine. From official sources, the results of calculations of the Ministry of Economic Development and Trade of Ukraine are presented, which evaluates it through integral index, according to the methods of "spending - retail trade", businesses losses, monetary, and the State Statistics Service of Ukraine within the System of National Accounts, which delivers indicator "non-observed economy". Unofficial estimates are presented by the World Bank.