Providing estimates for the cost-effectiveness of woodland creation in removing carbon dioxide from the atmosphere is a vital part of the evidence base on forestry’s contribution to mitigating climate change. Different estimates of cost effectiveness exist, but there have been inconsistencies in approach which can lead to confusion and misunderstanding. Therefore, it is important to understand how existing studies have been carried out in order to consider the most appropriate and consistent approaches to be used in future. This Research Note examines two recent studies which assessed the cost-effectiveness of forestry options for climate change mitigation across Great Britain. Four key elements in each study are reviewed: (1) the forestry options considered, including species planted, yield class and management (initial spacing, thinning regime, rotation length); (2) estimated carbon savings and emissions; (3) other benefits and costs; and (4) cost-effectiveness metrics. The review suggests that a primary reason for differences in cost-effectiveness estimates is different cost assumptions. However, underlying assumptions are not clearly laid out in each case, hampering direct comparison. The Note makes recommendations for further research to support future analysis and policy evaluation. Improved understanding and clarity in these areas will help to support robust and consistent approaches to estimating the cost-effectiveness of woodland planting in tackling climate change.