A number of studies have shown that the quality of life of two common interstitial lung diseases (ild), sarcoidosis and pulmonary fibrosis patients, is impaired and that fatigue is a substantial problem for those patients. Furthermore, breathlessness is an additional major problem in pulmonary fibrosis. In the field of cardiovascular disease and breast cancer, personality factors have shown to play a role in patient's morbidity, mortality, quality of life, fatigue, depressive symptoms, and one study showed a predictive role of personality factors in health care consumption. No studies examining personality factors have been performed in sarcoidosis or pulmonary fibrosis. Therefore, the aim of the present study is to examine the role of personality factors as predictors of fatigue, quality of life, prognosis, and health care consumption in sarcoidosis and pulmonary fibrosis. In this study a number of possible moderators, such as social support, will also be examined, aiming to get a full picture of the relationship between the various factors examined. Known and new sarcoidosis and pulmonary fibrosis patients (inclusion period 1 year) of ild care team of the outpatient clinic of the department of Respiratory Medicine of the University Hospital Maastricht will be asked to participate through completing questionnaires at baseline and every six months for 18 months, and allowing the researchers access to their medical records for the purpose of this study.