Risk management is critical for success in project-based industries, especially in the construction industry. In current literature, various risk-based decision support systems have been proposed to systematically identify and assess risks. However, majority of these systems use the risk ratings assigned by the decision-makers, mainly, probability and impact ratings, as input values and quantify the level of risk associated with the project based on these inputs. However, in majority of the cases, these ratings are assigned based on the subjective judgment of the decision-makers and highly depend on their level of knowledge, risk attitude and assumptions. This paper attempts to explore the process of assignment of risk ratings by the decision makers and question how the reliability of the risk assessment process can be enhanced in practice. In this effort, a risk mapping tool that has been developed by the authors is used to conduct a case study that explains how the risk ratings are defined by different decision makers and identify the reasons of possible divergence between assigned ratings. In this regard, a case study is conducted with three construction experts by using data of a real construction project and risk assessment exercise has been repeated using different strategies to collect expert opinion on risk ratings. The results of the case study show that although the subjectivity of ratings and sensitivity to risk attitude cannot be totally overcome, some strategies may be used to ensure a more reliable risk rating process. Those strategies mainly cover minimization of divergence of assumptions made by the decision-makers, clarifying what is included under the identified risk factors by defining sub-risk attributes and facilitating group decision-making. (C) 2014 The authors. Puplished by Elsevier Ltd.Open access under CC BY-NC-ND license. Selection and peer-review under responsibility of the IPMA.