This study critically appraises the contribution of cost-effectiveness analysis (CEA) in improving the rational allocation of healthcare resources in Ireland. While Ireland has successfully established some of the institutional infrastructure for CEA, there remain key areas for improvement: (1) Ireland has an explicit cost-effectiveness threshold of €45,000/QALY. It resulted from negotiations between the pharmaceutical industry and the public health service and only applies to pharmaceutical interventions. If Ireland is to use a threshold, it would be better served by an empirically determined threshold that applies to all interventions. (2) The threshold has recently been exceeded by a number of expensive drugs, in some cases by a very large margin. Conversely, despite being highly cost-effective, colorectal screening remains unimplemented due to a failure to allocate resources. In the absence of clarity around these decisions, the allocations appear to indicate that considerations of budget impact are dominating rather than complementing those of cost-effectiveness. (3) Recent CEAs by Ireland’s statutory health technology assessment authority, the Health Information and Quality Authority (HIQA), appear to confuse average cost-effectiveness ratios with incremental cost-effectiveness ratios (ICERs). Clarity around the interpretation of cost-effectiveness evidence is required to instil confidence in the process. (4) Ireland has an established CEA process to appraise new drugs. However, this process has been bypassed in recent cases, as some costly cancer drugs have been approved before being subject to CEA, despite recommendations that these drugs be assessed. Consistency in approach is required to instil confidence in the process. (5) Greater transparency around reimbursement decisions would be desirable, whereby the relevant bodies issue documentation explaining their decisions and deliberations. In conclusion, CEA could make a greater contribution to rational resource allocation in Ireland if more rigorous and consistent decision rules were applied. Greater accountability of the decision making process should further that goal.