Cancer in older people is an increasingly common problem. Since survival benefits may decline and the risks of treatment progressively increase with age, preservation and improvement of quality of life (QOL) is a major goal of geriatric oncology. The concept of health-related QOL holds that the preservation of health and physical function is necessary to the maintenance and improvement of QOL, and encompasses several constructs, including physical, functional, emotional, social, and spiritual domains. Several instruments for the assessment of QOL have been validated, but none has been calibrated to the special problems of older people. Such problems involve diverse evolution of health and disease around variable models, potential age-related shifts in values and focus, and barriers to the use of questionnaires, such as poor visual and auditory function, easy fatiguability, slower reactions and dementia. Individualised questionnaires may represent the ultimate goal in the assessment of QOL in the elderly. The assessment of QOL in general oncology has provided new and important information related to the value of breast preservation in the management of breast cancer, to the value of sexual function in the management of prostate cancer, and to the effects of limb amputation on QOL. Also, QOL at the beginning of treatment has independent prognostic implications. In geriatric oncology, assessment of QOL may allow trade-off between QOL and survival, and may determine the choice among alternative forms of life-prolonging and palliative treatments.