Purpose The once failed paid-for social question and answer (SQA) service is in full swing in China. The traditional profit model, which typically relies on advertising, is abandoned in this case. Instead, users have to pay for content and service. The purpose of this paper is to explore why users are willing to pay in paid-for SQA sites. Design/methodology/approach This study carried out 14 valid semi-structured interviews to investigate “why did they pay.” The interviewees are users of three popular paid-for SQA sites. The qualitative data were obtained from valid interviews and processed through thematic analysis. Findings The analysis revealed five overarching themes: paying for the answerer’s heterogeneous resource, paying for more credible answer, the cognition of the question, the price is affordable and expecting potential revenue. The five themes and their sub-themes constitute the motivation for why users would pay in paid-for SQA. Practical implications As a new business model for online information services, paid-for SQA sites are facing fierce competition from traditional ones. The findings not only indicate the importance of establishing a reciprocal network relationship among users, but also provide a better understanding of users’ needs and demands for paid-for SQA services. The results are helpful for paid-for SQA sites to conduct a differential competitive strategy according to the user’s paying motivation. Originality/value To authors’ knowledge, this is the first study, which provides primary-source data and valuable insights into users’ paying motivation in the context of new paid-for SQA sites in China.