Supply Chains (SC) encompass interfaces where several interactions occur, notablywith flows of services, products and information. Services play a major role in modern economies and its provision is widespread along the supply chain. This piece of research utilizes the Gaps Model of Service Quality, which is based on the disconfirmation paradigm, and relates it with lean principles of waste from a supply chain perspective. The Gaps Model analyses several gaps that might occur within organizations, leading to discrepancies between expected service and perceived service. A methodology is proposed for assessing the internal failures contributing to each gap of the original model. A second stage includes an approach inspired on QFD’s (Quality Function Deployment) matrices, envisaging a joint analysis of gap’s structure and supply chain’s failures, what allows computing the importance of each failure from a service quality perspective. Furthermore, these failures can be associated to lean wastes, thus providing a framework for “leanliness” assessment. A simplified example for a generic supply chain is also presented.