The aim of this study was to investigate the effects of various clinical, laboratory characteristics, and therapeutic modalities on the survival of patients with malignant pleural mesothelioma. One hundred consecutive patients with a pathologically proven diagnosis of malignant pleural mesothelioma treated between 1993 and 2005 were included in the study. Using a Cox proportional hazard model, comorbidity, weight loss, breathlessness, and performance status were identified as independent prognostic factors. Comorbidity had interestingly favorable effect on the survival. Treated patients with chemotherapy had significantly longer survival than those treated with best supportive care. However, it was necessary to complete at least 6 cycles for a survival benefit. In conclusions, comorbidity information should be recorded in the recent prognostic studies. The drugs used for the comorbidity may improve survival.