In this master’s thesis the budget of the State Social Insurance Fund of the Republic of Lithuania is examined in comparison with the state budget of the Republic of Lithuania. The analyses of the process, income and incurred expenditure of the State Social Insurance Fund budget are included. Main similarities and differences of both budgets are analysed and controversy for merging discussed. In the first part of this thesis the concept of the budget in the sense of public finance law and tax law is analysed and the concept of consolidated budget examined. Moreover, the system of state extra-budgetary funds established in Lithuania is presented, identifying the legal bases and purpose of the establishment of each fund. The criteria to be me...