Qualitative research methods, primarily interviews, have become more common in the field of addiction research. Other data sources were often neglected, although sources such as social media can offer insights into the realities of people, since social media also plays a relevant role in today's living environments. This article examines the use of online forums as an underutilized data source in contrast to telephone interviews, to identify methodological opportunities and challenges. We analyzed nine discussion threads and seven interviews about ‘alcohol consumption during pregnancy’. Discursive comparison of the results was performed with a focus on sampling issues, comparability and risks for participants and researchers. Key issues were present in both data sources. People with different opinions were openly hostile in forums, while tolerance was more often expressed in interviews. The interviews showed a rather mild communication style, which could be attributed to social desirability. In the forum discussions, the participants often expressed themselves very directly. To comprehensively grasp the subject matter of the research, it is important to recognize the types of communication promoted by different data sources. These results have implications for research about female substance use. Knowledge of the issues will bestow a valuable contribution to researchers working in the field of substance use to help develop appropriate research approaches, as they engage in research into this highly stigmatized and controversial area.