Aims!#!To compare diabetes patients with hyperglycaemic hyperosmolar state (HHS), diabetic ketoacidosis (DKA), and patients without decompensation (ND).!##!Methods!#!In total, 500,973 patients with type 1 or type 2 diabetes of all ages registered in the diabetes patient follow-up (DPV) were included. Analysis was stratified by age (≤ / > 20 years) and by manifestation/follow-up. Patients were categorized into three groups: HHS or DKA-during follow-up according to the most recent episode-or ND.!##!Results!#!At onset of diabetes, HHS criteria were met by 345 (68.4% T1D) and DKA by 9824 (97.6% T1D) patients. DKA patients had a lower BMI(-SDS) in both diabetes types compared to ND. HbA1c was higher in HHS/DKA. During follow-up, HHS occurred in 1451 (42.2% T1D) and DKA in 8389 patients (76.7% T1D). In paediatric T1D, HHS/DKA was associated with younger age, depression, and dyslipidemia. Pump usage was less frequent in DKA patients. In adult T1D/T2D subjects, metabolic control was worse in patients with HHS/DKA. HHS and DKA were also associated with excessive alcohol intake, dementia, stroke, chronic kidney disease, and depression.!##!Conclusions!#!HHS/DKA occurred mostly in T1D and younger patients. However, both also occurred in T2D, which is of great importance in the treatment of diabetes. Better education programmes are necessary to prevent decompensation and comorbidities.