There is increasing recognition of the need to assess the impact of colorectal cancer and its treatment on patients' quality of life (QL). An overview is provided of generic and (colorectal) cancer-specific QL questionnaires that yield adequate levels of reliability and validity. These measures have been or could be used in clinical research settings among colorectal cancer patients. Additionally, QL-based studies in colorectal cancer aimed at identifying the most optimal (cost-) effective treatment, or the parameters that best predict objective outcome, are described and exemplified. As is illustrated, QL data complement clinical outcomes and are essential to further improve the treatment and care of colorectal cancer patients and to support decision-making.