Despite the increasing interest of Lithuanian health care professionals in measurement of health-related quality of life, there is a lack of medical literature in Lithuanian that describes methodological issues of quality of life assessment. Main psychometric properties of questionnaires (validity, reliability, and responsiveness), as well as methods of their establishment are discussed in this review of international literature. Criteria for selection of a measurement instrument are provided, issues of interpretability of scores and "minimal clinically significant difference" are described in this article. Increase in demand of health-related quality of life questionnaires across medical specialities during the last decade and problems of cross-cultural adaptation of instruments are briefly reviewed.