Although previous authors have reported single data point, yearly changes in respiratory function have not been examined in combined pulmonary fibrosis and emphysema (CPFE). To quantify the annual changes in respiratory function of patients with CPFE and to examine the difference in survival between CPFE patients and patients with idiopathic pulmonary fibrosis without emphysema (IPF alone), 26 patients with CPFE and 33 IPF alone patients, whose respiratory function had been monitored for at least a year, were selected. The baseline of vital capacity percent predicted (VC% pred) in CPFE patients was greater than that in IPF-alone patients (86.6+/-24.0% vs. 72.8+/-19.4%, p=0.018). The annual decrease in VC% pred was significantly less in CPFE patients than in IPF-alone patients (-1.2+/-4.8% vs. -8.0+/-7.4%, p<0.001). Baseline ratio of forced expiratory volume in one second to forced vital capacity (FEV(1)/FVC%) in CPFE patients was lower than that in IPF-alone patients (76.6+/-8.5% vs. 85.2+/-6.7%, p<0.001). In the CPFE group, FEV(1)/FVC% tended to decrease with time (-0.5+/-2.2% per year), but, in contrast, it increased in IPF-alone patients (+1.1+/-3.4% per year) (p=0.036). Baseline of diffusing capacity percent predicted (DLco% pred) was significantly lower in CPFE patients than in IPF-alone patients (45.3+/-15.0% vs. 60.7+/-19.8%, p=0.003). The annual decrease in DLco% pred was lower in CPFE patients than in IPF-alone patients (-3.7+/-7.9% vs. -10.7+/-8.8%, p=0.042). There was no significant difference in the survival duration between 26 CPFE and 33 IPF-alone patients according to Kaplan-Meier analysis. Ventilatory and gas-exchange deterioration during the course of IPF became mild when emphysema was coexistent.