Quality requirements, i.e. those requirements that pertain to a system's quality attributes, are traditionally regarded to be useful only when they are represented quantitatively so that they can be measured. This article presents a value-oriented approach to specifying quality requirements that deviates from the classic approach. This approach uses a broad range of potential representations that are selected on the basis of risk assessment. Requirements engineers select a quality requirement representation such that they get an optimal balance between mitigating the risk of developing a system that doesn't satisfy the stakeholders' desires and needs on the one hand and the cost of specifying the requirement in the selected representation on the other hand. This issue is part of a special issue on quality requirements.