Numerous reports of the effectiveness of methadone in reducing opiate use as well as mortality, criminality, prostitution and the risk for HIV-infection have been published during the last forty years. However, poor adherence to treatment, continuing drug use and increasing rate of premature termination may lead to less than optimal outcome results or in too many cases death. The aim of this paper is to investigate which of the background variables, collected at the admission procedure, that can be used to tell which type of patient will adhere to the treatment regime and succeed or who will fail and who either need special considerations or ought not to be accepted for a methadone treatment (MMT). As much as 86 percent of the compliers in this study did benefit from the treatment and were rated as medium to very much improved according to CGI-I. The group not improved or worse had significantly more background problems such as school problems, a history of non-opioid abuse, many non-MMT treatment episodes, low age at drug debut and opioid debut than the group much or very much improved. Those moderately improved is usually situated somewhere in between the others.