The term regional security dialogue brings to mind state-organised conferences and events; however, an under-appreciated subset of such dialogues are organised by non-state actors that have unique formal aspects. These quasi-formal dialogues operate alongside, and sometimes in competition to, state-sanctioned processes. Why do some of these forums appear to be more effective at fostering regional dialogue than strictly formal or informal processes with the same goals? Drawing from heterogenous discourse approaches, we address this question by identifying and expanding the concept of the quality of discursive space, as a key feature for the success of security dialogues. We then apply this concept to two of the most successful so-called Track 1.5 security dialogues: the Munich Security Conference (MSC) in Europe and the Shangri-La Dialogue (SLD) in Asia. We analyse these cases using a mix of interviews with participants and organisers, participant observation, and public outputs with the aim of improving the understanding of the role and impact of Track 1.5 diplomacy in the practice of international security. Our findings highlight that it is what we call the quality of discursive space, as a mix of different components in this space, which differentiates effective dialogues from mere policy ‘talk shops’.