Abstract Introduction: There is a strong relationship between the accurate medical diagnosis and appropriate treatment. Any disagreement between admission diagnoses (ADx) and discharge diagnoses (DDx) can lead to medical error. Because of high incidence rate of cardiovascular disease in Zanjan province, this study aimed to determining the Discrepancies between admission diagnoses and discharge diagnoses. Method: This is a cross-sectional and descriptive-analytical study that conducted at Zanjan province in the period from 2012 to 2018. The sample limited to patients whom The ADX and DDX codes of ICD-10 were between I00 and I99. Data analyzed by using R (v3.6.0) and Rstudio (v1.2.1335) software. Agreement analysis was conducted using Cohen’s Kappa statistics and the Chi Square statistic is used for testing relationships between variables. Results: Agreement analysis of CVDs subgroups showed that the value of the Kappa coefficient range were from κ = 0.34 for Chronic rheumatic heart diseases to κ = 0.93 for Acute rheumatic fever diseases. The values of the Kappa coefficient for the 10 most CVDs ICD-10 codes were in the range from κ = 0. 44 for I25.9 to κ = 0. 77 for I80.2. Conclusion: ICD-10 diagnostic codes that recorded in the HIS can be a reliable factor to evaluate the ADX and DDX discrepancies. The findings of this study may help to understand the cause of the differences in the qualities of health care in the hospitals. Keywords: patient admission, patient discharge, diagnosis, cardiovascular disease, international classification of diseases.