Background: Dyspnoea (breathing difficulty) is a common reason why patients are in need of pre-hospital care provided by ambulance clinicians. Within the pre-hospital field, knowledge among patients with dyspnoea is still limited even though it is caused by several serious underlying medical conditions. Aim: To describe characteristics and prediction of an adverse outcome among patients with dyspnoea, assessed by ambulance clinicians. Methods: A retrospective observational study including patients aged ≥ 16 years during 2017 in Sweden. In all, 6354 ambulance missions were included.  Data were manually collected through  ambulance- and hospital records.  Descriptive statistics and multiple logistic regression were used. Results:  Mean age was 73 years, 56% were women. There were more than 400 different final diagnostic codes where chronic obstructive pulmonary disease (20.4%), pulmonary infection (17%), and heart failure (15%) were most common. In all, 84% had previously experienced dyspnoea. The overall 30-day mortality was 11%. Among  patients with a time-sensitive final diagnosis (13%),  27% died within 30 days. The most frequent  time-sensitive diagnoses were cardiac diseases (4.1% of all diagnoses), infectious/inflammatory diseases (2.6%), and vascular diseases (2.4%).  Hypertension, renal disease, symptoms of pain, abnormal respiratory rate, impaired consciousness, a pathologic ECG and a short delay until calling the emergency number predicted an increased risk of a time-sensitive final diagnosis. Increasing age, renal disease, cancer, low systolic blood pressures, impaired consciousness and abnormal body temperature predicted an increased risk of death. Conclusions: Patients with dyspnoea often show a complexity of symptoms and signs. They have a coexistence of several chronic diseases and a high risk of death.  Underlying life-threatening conditions are common.Thus, a great burden are placed on ambulance clinicians who are responsible for the pre-hospital care.