Background and purpose: Proper diagnosis of patients with COVID-19 is one of the challenges in medical centers. RT-PCR is the standard and reference test in diagnosis of patients with COVID-19. This study aimed at accelerating the correct diagnosis of COVID-19 and the diagnostic power of chest CT scan and RT-PCR. Materials and methods: This study was performed in 569 patients with COVID-19 admitted to Golestan-Kermanshah Hospital based on diagnostic chest CT scan. The RT-PCR test was considered as the standard and reference test in diagnosis of COVID-19. Relevant information was extracted from patients' records using a researcher-made checklist. Data analysis was performed in STATA V14. Results: The mean age of patients was 52. 53±, 16. 88 years. Men included 432 (75. 9%) patients. In this study, 84% had positive chest CT scan and 84. 9% had positive RT-PCR results. Sensitivity, specificity, and accuracy of chest CT scan were 88. 7%, 64. 8%, and 80. 1%, respectively. The sensitivity of chest CT scan was 89. 9% in people under 60 years of age and 82. 8% in patients over 60 years old. The accuracy of chest CT scan was 84. 7% in women and 78. 7% in men. Conclusion: The accuracy of chest CT scan is high in patients with COVID-19 while it cannot definitively detect or rule out COVID-19. Nevertheless, it can be used as a quick tool to classify patients into positive and negative groups.