AIMS: To review the current research of hidden populations of illicit drugs users using web-based methods and discuss major advantages and disadvantages. METHODS: Systematic review of 16 databases, including PubMed, PsycINFO EBSCOhost, CSA Sociological Abstracts, Expanded Academic ASAP and Google Scholar. FINDINGS: Substances researched were most commonly 'party/club drugs' such as ecstasy and cannabis. All of the studies reviewed concluded that the internet is a useful tool for reaching hidden populations, but is likely to impose some bias in samples. Advantages include: access to previously under-researched target groups speed international applications increased ease of data entry and improved confidentiality for respondents. The major disadvantage is a lack of representativeness of samples. CONCLUSIONS: Internet research is successful at accessing hidden populations of illicit drugs users, when appropriately targeted and provides unprecedented opportunities for research across a wide range of topics within the addictions field. Findings are unlikely to be generalisable to the general public, but appropriate for describing target populations.
