Performance status (PS) is a standard functional classification in oncology research and practice. However, despite its widespread use, little is known about the prevalence of poor PS in lung cancer patients, in relation to other cancers, based on the assessments of health care providers and patients. Data from two quality of life studies were pooled for analysis. Analyses were performed on the subset of patients with lung cancer (n = 503) from the entire population of cancer patients (n = 2885). The prevalence of poor PS (defined as PS = 2-4 on a 0-4 scale) was determined for lung cancer patients. Prevalence of poor PS among lung cancer patients was 34% when estimated by providers and 48% when estimated by patients themselves. Agreement between providers and patients was only fair (weighted [kappa] = 0.41). For both advanced and early stage disease, lung cancer patients were at the highest risk for poor PS compared with other common cancers. The prevalence of poor PS is quite high in lung cancer patients. Providers tend to underestimate poor PS. Specific clinical trials and treatment guidelines for this patient population are urgently needed.