Background & objectives: Optimal use of available resources is one of the challenges for all the hospital managers. One proposed solution for this problem is reduction of the average duration of hospitalization. The purpose of this study was to identify factors affecting long-stay hospitalizations. Methods: This cross-sectional survey was done on medical records of 370 randomly selected inpatients in Sina hospital in 2013. Data collection tool was researcher-made form. Data analysis was done by STATA software. Results: The median of LOS in the studied hospital was 4 days. Minimum and maximum of LOS was 1 and 60 days, respectively. Factors such as age (p= 0.04), job (p=0.03), type of disease (p= 0.04), hospitalization ward (p= 0.03) and discharge status (p= 0.04) significantly affected the average length of stay. Among the age groups the highest odds ratio (OR =2.09) belonged to 60-79 years age group. In terms of discharge status patients that need to follow up at discharge time had the highest odds ratio (OR = 1.8). Conclusions: In order to better manage the LOS indicator, care providers must identify the factors affecting this indicator and then towards these manageable identified factors implement principal measures to take advantage of all the hospital beds.