Background Telephone triage at emergency medical dispatch centres is often challenging for registered nurses due to lack of visual cues, lack of knowledge about the patient, and time pressure - and making the right decision can be a matter of life and death. Some calls may be more difficult to handle, and more knowledge is needed about these calls to develop education and coping strategies. Therefore, the aim of this study was to describe the perspectives of registered nurses' views about managing difficult calls to emergency medical dispatch centres. Methods A descriptive design with a qualitative inductive approach was used. Three dispatch centers in mid-Sweden were investigated, covering about 950,000 inhabitants and handling around 114,000 calls per year. Individual interviews were carried out with a purposeful sample of 24 registered nurses. Systematic text condensation was conducted. Results Seven themes were generated: calls with communication barriers, calls from agitated or rude callers, calls about psychiatric illness, calls from third parties, calls about rare or unclear situations, calls with unknown addresses and calls regarding immediate life-threatening conditions. There was a strong consensus among the registered nurses about which calls were experienced as difficult, with the exception of calls about immediate life-threatening conditions. Some registered nurses thought calls about immediate life-threatening conditions were easy to handle as they simply adhered to protocol, while others described these calls as difficult and were emotionally affected. Conclusion The registered nurses' descriptions of difficult calls focused on the callers, while their own role, the organisational framework, and leadership were not mentioned. Many types of calls included difficulties, which could be related to the caller, their symptoms, or different circumstances. The registered nurses pointed to language barriers and rude, agitated callers as increasing problems. An investigation of actual emergency calls is warranted to examine the extent and nature of such calls.