This is the registry of control participants for patients with various respiratory diseases. We screened healthy volunteers who visited Seoul National Hospital Healthcare System Gangnam Center for routine health check-up, and enrolled patients who agree to participate in the study. The participants undergo baseline questionnaires, provide blood specimen and information of the results of health check-up. We will include participants as controls if they have no significant respiratory symptom and no significant radiographic abnormality. The data from this registry will be compared with those from other registry of various respiratory diseases