This paper presents a model that explains why and when buyers and suppliers may differ in the ways they perceive certain relationship attributes. Understanding when buyers and suppliers will share perceptions, and when not, can help future researchers in deciding how to measure these attributes. The paper analyses survey data from 86 dyadic buyer-supplier relationships, involving 388 respondents. Our results indicate that buyers and suppliers form different perceptions of attributes that are closely related to the identity of their firms, such as supplier performance, or, of attributes about which they have different information, such as technology uncertainty. Moreover, we found that also the associations between attributes differ significantly between buyers and suppliers. Our results suggest that, for some attributes, key informants from the supplier side will deliver the most reliable information whereas, for other attributes, the buying side will deliver the most reliable data. Further, not only do buyers' and suppliers' perceptions of particular attributes differ, the way these attributes are associated with each other also seems to differ, which may have important implications for theory development in the field of supply chain management. For future research we recommend to use objective data where possible. If this is not possible use the perceptions of the best informed party or the party whose identity is least related to the construct to measure. Further, we recommend using additional research methods that result in similarity of perceptions. Finally, we suggest using ex-post statistical remedies.(C) 2012 Elsevier B.V. All rights reserved.