The paper discusses the use of what are known as tax expenditures in various member countries of the Organization for Economic Cooperation and Development (OECD), with a view to analyzing the scope of state aid in these countries. Tax expenditures are defined as losses to the Treasury from granting certain deductions, exemptions, or credits to specific categories of taxpayers. Tax breaks are one method that the government uses to promote certain policy objectives. Tax expenditures are an alternative to direct government spending on policy programs. A specific feature of this type of assistance is that it takes place through the revenue side of the budget and not through direct spending. In most countries, government revenue is predominately generated from taxes. This explains why tax expenditures are usually part of the tax system and take the form of various tax breaks, exemptions, deferments or credits. Their use leads to reduced tax burdens, thus being a hidden form of subsidizing specific policy objectives or groups of taxpayers. This invariably leads to a situation in which an increased part of public spending spins out of control and is not subject to standard budgetary rules, the author says. This form of assistance needs to be identified and evaluated properly, Wyszkowski says, because it leads to a lack of transparency in the government’s policies with regard to businesses and the public. The author analyzes this method of subsidizing in comparison with direct spending from the budget. In some cases, the use of tax expenditures in the tax system may prove to be more expensive than direct spending from the budget, according to Wyszkowski. An analysis of tax expenditures helps determine the effectiveness of specific government policies. This is especially important in the context of the ongoing debate on reforming the public finance system, Wyszkowski says.