Although functional status serves as a major predictor of morbidity, researchers and clinicians use different terms and measures, limiting comparisons across studies. To demonstrate how differing measures may generate varied findings, we compared and contrasted data from the SF-12 Health Survey Physical Component Summary Scale (SF-12 PCS) and the Enforced Social Dependency Scale (ESDS). The sample consisted of 49 women aged 65 and older recovering from gynecological cancer surgery with data collection at baseline (postoperative period) and then at 3 and 6 months. Analysis of the relationship between SF-12 PCS and ESDS over time using generalized estimating equations (GEE) demonstrated the relationship was less than 1.0, signaling less than perfect agreement between measures (β = 0.16, P =.002). These findings suggest that that the 2 measures are not interchangeable and may produce conflicting evidence. This highlights the importance of researchers’ and clinicians’ careful conceptualization and operationalization of functional status before measure selection.