The study examined whether the items of the World Health Organization Quality of Life—Brief questionnaire can assess its four underlying domains (Physical, Psychological, Social, and Environment) in a sample of lung cancer patients. All patients (n = 1150) were recruited from a medical center in Tainan, and each participant completed the World Health Organization Quality of Life—Brief. Several Rasch rating scale models were used to examine the data-model fit, and Rasch analyses corroborated that each domain of the World Health Organization Quality of Life—Brief could be unidimensional. Although three items were found to have a poor fit, all the other items fit the unidimensionality with ordered thresholds.