Life cycle assessment (LCA) is used by practitioners and policy-makers to help them understand the sustainability impacts of packaging. LCA is useful because it quantifies the impact of a product throughout its life cycle, from raw materials extraction through to disposal or recovery. However, it can only ever be one input to decisions about the design or procurement of packaging. LCA has limitations as a tool to measure environmental impact and it does not currently evaluate social or financial impact. This paper provides a critical review of the role of LCA in evaluating packaging sustainability. It does this by evaluating the results of LCA studies that compare different types of carry bags and their implications for policy and practice. The benefits and limitations of this type of analysis are discussed. The case study of plastic carry bags demonstrates that while a scientific understanding of life cycle impacts is essential to support informed decision-making, a broader sustainability analysis is required to ensure that all relevant issues are considered. These include the functionality of alternative bags, their relative cost, convenience for consumers and retailers, and the availability of reuse and recovery systems. An alternative approach, which evaluates packaging design within a broader sustainability framework, is presented and discussed. Copyright © 2010 John Wiley & Sons, Ltd.