Background: Physical and psychological stresses produced by diagnosis and treatment of cancer can lead to positive psychological changes or posttraumatic growth. The aim of current study is to assess posttraumatic growth and its dimensions in Iranian patients with cancer, and the impact of demographic characteristics on posttraumatic growth.Methods: This was a descriptive study on 452 patients with cancer who referred to the oncology wards of two main hospitals in Tehran, Iran. The instruments were the Demographic Characteristics Scale and the Posttraumatic Growth Inventory. SPSS version 15 was used to analyze the data. Results: The mean age of participants was 46.2±14.2 years, 59% were female and 39% had metastatic cancer. The mean PTGI score of the participants was 68.6±14.6. The most acquired percentage of score was for "spiritual changes" and "communication with others". Age, educational status, income, and type of cancer had significant correlation with posttraumatic growth score.Conclusion: The findings of the current study indicated that the score of posttraumatic growth in Iranian patients with cancer was higher than in patients of Western societies. The most improvement was seen in the "spiritual changes" dimension.