This article examines the Irish experience of spending reviews and seeks to identify key lessons that should enhance the effectiveness of this process both in Ireland and in other OECD countries. Since the beginning of the economic and financial crisis, spending reviews have played an important role in Ireland’s efforts to restore expenditure policy to a more sustainable footing. However, the purpose of future reviews will move from improving the deficit position to ensuring all expenditure is considered when Government is making budget decisions. The purpose of spending reviews is to increase the fiscal space available to government for new, high priority, policies. By systematically examining baseline expenditure using available evidence and data, the increasing tendency to focus only on incremental improvements in expenditure can be countered. Spending reviews should be used to further embed the principles of expenditure efficiency and effectiveness into the wider budget process. This can be facilitated through extending the availability of relevant evaluations and performance information and ensuring such evaluations become central to the budgetary process.