Objective: To clarify what future problems must be resolved and how clinical findings of SARS-CoV-2 infection differ from those of cHCoV infection. Methods: Patients and Methods Clinical characteristics of 14 patients with laboratory-confirmed Coronavirus disease 2019 (COVID-19) and 5 patients with cHCoV pneumonia admitted to our institution and treated up to March 8, 2020, were retrospectively analyzed. Results: On admission, 10 patients had pneumonia, 5 of whom had pulmonary shadows detectable only via computed tomography (CT). During hospitalization, another patient with no pulmonary shadows on admission developed pneumonia. In total, 11 (78.6%) of the 14 patients developed pneumonia, indicating its high prevalence in COVID-19. During hospitalization, the patients' symptoms spontaneously relapsed and resolved, and gastrointestinal symptoms were frequently found. C-reactive protein values showed correlation with the patients' clinical courses. Ritonavir/lopinavir were administered to 5 patients whose respiratory conditions worsened during admission, all of whom improved. However, the pneumonia in the 6 other patients improved without antivirals. None of the 14 patients died, whereas 5 other patients with cHCoV pneumonia were in respiratory failure on admission, and one patient (20%) died. Conclusion: Both SARS-CoV-2 and cHCoV can cause severe pneumonia. Problems for future resolution include whether antiviral agents administered in cases of mild or moderate severity can reduce the number of severe cases, and whether antivirals administered in severe cases can reduce mortality.