Objective In most UK ambulance services, crews attending someone who has phoned the emergency services on ‘999’ will take the patient to hospital, unless the patient makes the decision to stay at home (or wherever they happen to be when the ambulance arrives). Safety concerns have been raised about non-conveyance decisions. Weunder took a study of one UK Ambulance Service to examine ambulance crew members’ views on how decision-making about non-conveyance works in practice in relation to non-urgent calls. Methods A total of 25 paramedics took part in three focus groups. Focus groups were transcribed and analysed thematically. Results The ambulance service's apparently straight forward guidance on decision-making about non-conveyance proved tricky in the messiness of the real world, for two reasons. The first was to do with the notion of the patient's capacity to make decisions and how this was interpreted. The second was to do with the complexity of the decision-making process, in which the patient, the crew and, in many cases, family or carers often take part in negotiation and de facto joint decision-making. Conclusions There is a mismatch between policy and practice in relation to non-conveyance decisions. Findings should be built into research and service development in this rapidly changing field of practice in emergency and/or unscheduled care. The commonly accepted perspective on shared decision-making should be extended to include the context of ‘999’ ambulance calls.