This article characterises the questioning behaviour in reference interviews preceding delegated online searches of bibliographic databases and relates it to questioning behaviour in other types of interviews/settings. With one exception, the unit of analysis is the question (N=610), not the interview. The author uses A.C. Graesser's typology of questions to analyse type of question and M.D. White's typology of information categories to determine the question's content objective; this is the first application of Graesser's typology to interview questions in any setting. Graesser's categories allow for a more subtle understanding of the kind of information need underlying a question. Comparisons are made between questions asked by the information specialist and those asked by the client. Findings show that the information specialist dominates the interview, about half the questions were verification questions and about 22% were judgemental questions or requests; all but four types of questions from Graesser's categories appeared in the interviews, but no new question types were discoverd. Clients often phrase questions as requests. In content, both clients and information specialists focus on the subject and service requested, but the clients ask also about search strategy and output features. Both parties ask predominantly short-answer questions. Results are related to interface design for retrieval systems.