Many factors affect tobacco quit rate. In this study we investigated the abstinence rate after 5 years based on the age of smoking initiation. This pre-post field trial study was conducted on 398 smokers who participated voluntarily in a smoking cessation clinic in 2005. They were followed for 5 years and their success or failure in continuous abstinence was evaluated and recorded in 2010. Three hundred and five participants (76.6%) succeeded at the end of the course. Follow up at the end of 2010 revealed that 111 (27.8%) cases were still maintaining their continuous abstinence after 5 years including 64 men and 47 women. The mean age of smoking initiation in successful and failed subjects was 21.9 and 20.7 years respectively. The age of smoking initiation could be a predictor of maintaining abstinence in the future. Starting smoking at an earlier age could have a negative effect on long-term abstinence.