PurposeThis study aims at exploring users' motives to form attachments within the social Q&A community context and identifying the differences between active users and lurkers when building emotional attachments. By utilizing the media system dependency (MSD) theory, this study investigates into the driving factors of dependency relations (understanding, orientation and play) to user attachments (i.e. attachment to the social Q&A community, attachment to content creators).Design/methodology/approachThe research model is empirically validated by an online questionnaire among users of a social Q&A community. Deriving from the actual behavioral data, the authors divide 262 valid responses into 157 active users and 105 lurkers according to whether they post or not. The partial least squares (PLS) method is exploited to analyze the relationships in the model. In addition, the PLS-based multi-group analysis is conducted for comparing active users and lurkers.FindingsThe empirical results confirm that dependency relations (understanding, orientation and play) significantly influence user attachments. Multi-group analysis suggests that the effect of understanding dependency relations on attachment to content creators is stronger for active users than for lurkers. However, the effect of orientation dependency relations on user attachment is significant for lurkers but not significant for active users.Originality/valueThis study enriches the knowledge of the MSD theory by extending it to the social Q&A community setting. Based on the MSD theory, the relationships between three sides of dependency relations and two types of user attachments are hypothesized in the research model. Besides, the impact of user heterogeneity in building user emotional attachment still lacks consideration. This study is one of the first in the field of comparison studies to compare active users and lurkers in such context, providing a novel contribution in understanding the motivations and emotional responses of different users.