BACKGROUND.  Shared decision-making is one widely cited model of patients’ participation in decision-making about their own healthcare.  This study aimed to deepen our understanding of the concept of shared decision-making, as it was defined by Charles et al, when two situations arose in consultations:  when information was not exchanged, and when third parties were involved. RESULTS AND DISCUSSION.  For a range of reasons, there were occasions when information was not exchanged, by patients and health professionals, about the patients’ problem or about treatment options.  No consistent relationship between the information not exchanged and patients’ satisfaction with the information given and/or the option selected could be identified.  The addition of a problem definition stage to the model is proposed and some amendments to the model are suggested to compensate for situational factors that may be important in deciding if all information relevant to decision-making has been exchanged. Four types of third party were involved in consultations in various ways and for various reasons.  When third parties were involved, each stage of the decision-making process could look different from the dyadic conceptualisation, e.g. information could flow in various directions and the deliberation could involve coalition formation.  Furthermore, the amount of information exchanged could be hindered or encouraged.  If third parties were involved in consultations the process decision-making may look different from the dyadic conceptualisation.  Although looking different, the decision-making process may still be C-SDM but it may be masked by additional clutter and/or the notion of sharing a decision may be different. CONCLUSIONS.  The concept of C-SDM may be considerably more complex than the current theoretical portrayal in the literature.  Some additions and amendments to the representation of C-SDM are proposed and these may make C-SDM (even more) difficult to implement, teach and measure in practice.