Information exchange between patients and health professionals is fundamental to achieving patient participation in decision-making and shared decision-making is said to require the exchange of "all information relevant to decision-making". This paper reports on a qualitative investigation of instances in which information that was potentially relevant to decision-making was not exchanged in consultations. Consultations from 5 diverse clinical areas in the UK were video-recorded and the health professionals and patients involved were interviewed separately before and after their consultations. This analysis is based on cases involving 20 patients. It draws on data from their 26-recorded consultations and from the 137 associated interviews. Several strategies were used to identify instances in which patients and/or health professionals did not disclose information that was potentially relevant to decision-making. Analysis focussed on the types of information not disclosed, the reasons that health professionals and patients gave for non-disclosure, and the apparent or potential significance of the non-disclosure. We identified 34 instances of non-disclosure of information relating to the patient's problem and 52 instances of non-disclosure of information relating to treatment or management options. The types of information not disclosed were diverse and the reasons given for non-disclosure varied. Some, but not all, instances of non-disclosure had negative implications for the quality of decision-making and/or the patient's healthcare experience. Our findings have implications for future attempts to examine information exchange in consultations-whether for research or for professional assessment purposes. In particular, they highlight the importance of appraising instances of non-disclosure of information in context and of recognising the limitations of approaches that rely on single consultations and/or single perspectives for assessments of information exchange.