Abstract: Cancer can be defined as the uncontrolled growth of malignant cells. Today, cancer is the second most common cause of death in the world. This study aimed to determine the frequency of cancers and their demographic characteristics (cancer type, gender, age, location and family history) in cancer patients referred to Omid medical center of Urmia City. This study is a cross-sectional and retrospective. The records of 2972 patients referred to Omid hospital of Urmia (Northwest of Iran) in 2010 and 2011 were used. To make easy data analysis, the patients were classified based on age in the age groups of younger than 20, 20-40, 40-60, 60-80, 80-100 and older than 100. Then, the information from the questionnaires was entered in SPSS Software and analyzed. The mean age of the population was 17.80±55.33 years old. The 52.3% of patients were men. In this study, the youngest person were a 2 years old girl and a 2 years old boy and the oldest one is a 107 years old woman. The most common cancers were breast cancer (16.4%), esophageal cancer (11%), stomach cancer (9.7%) and lung cancer (8.5%). The breast, esophageal, stomach and lung cancers were most common in the age group of 20-40 (24.18%), 60-80 (16.8%), 60-80 (12.7%) and 60-80, respectively.