This article reports on the findings of a study involving intensive interviews with 21 former drug addicts who had successfully maintained abstinence for periods ranging from one-and-a-half to four years. They were among the 74 successful former drug addicts out of a pool of more than 2,000 participating in a major rehabilitation program in Hong Kong in 1996. The intensive interviewing primarily employed a Q-sort task which required respondents to rate the importance of causes leading to their success in abstinence maintenance. The pool of causes was derived from ten theories that claim to explain drug abuse and recovery. Results show that the cognitive-developmental factor was the most important one followed by the social cognitive factor, which was significantly more important among former addicts who had maintained abstinence for longer time. These findings, therefore, uphold the particular relevance of cognitive factors to rehabilitation.