The purpose of this study was to determine whether the Functional Assessment of Cancer Therapy-Colorectal (the FACT-C), a disease-specific tool for the assessment of colorectal cancer patients' QOL, is a valid assessment tool for measuring QOL changes. Ninety-eight colorectal cancer patients performed the assessment at baseline and 52 of these patients completed the instrument at one month and six months after colectomy. In addition to the FACT-C, the shortened forms of the Profile of Mood States, the Eastern Cooperative Oncology Group Performance Status Rating, Neuroticism Scale in the Eysenck Personality Questionnaire, and Functional Living Index-Cancer were completed. We found convergent and divergent validity and good reliability of the FACT-C. Patients' overall QOL was lower at one month after colectomy and recovered to the pre-surgery level at six months after colectomy.