The aim of this study was to study the relationship between physician-assessed quality of life parameters, i.e., toxicity and physical performance, and patients' self-reports of their quality of life (QoL). QoL was assessed at baseline and before each treatment, using the EORTC QLQ-C30. The WHO performance score (PS) and toxicity were assessed in physician interviews. The correlations between the WHO PS and the QLQ-C30 functioning scale scores varied from weak to moderate, depending on the scale. Strongest associations were found in physical-, social-, and role functioning, and in the global QoL. The QLQ-C30 nausea/vomiting and diarrhea scales correlated moderately to corresponding WHO scores. A multiple linear regression analysis was used to analyze the contribution of WHO PS and toxicity variables to the global QoL. The best model explained only 16% of the variance of the global QoL score. The present findings highlight the importance of independent QoL assessments focused on those aspects of QoL not captured in clinical interviews with the physician.