Investigator-derived quality of life (QoL) instruments such as the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire do not allow participants to weight the relative importance of QoL domains. We investigated the effect of allowing patients the ability to weight the relative importance of the five areas included in the FACT-P (Physical, Social, Emotional and Functional well-being, and Additional concerns). Patients (n=150) completed the FACT-P and gauged the relative importance of each QoL domain using a direct-weighting approach. This was then used to provide an adjusted Hybrid QoL score. Patients also completed a Visual Analogue Scale. Patients considered Social well-being to be the most important domain and Additional concerns to be the least important. When patient weightings were taken into account overall QoL scores increased. The validity of the Hybrid score was supported by its ability to distinguish between patients with metastatic and locoregional disease and its ability to detect expected decreases in global QoL over time. Application of the direct-weighting approach to the FACT-P allows assessments to more accurately reflect individual QoL. Unadjusted QoL scores may lead researchers to incorrectly estimate the true QoL of respondents.