The diagnosis and management of paediatric Cushing syndrome (CS) is highly challenging. This study aims to characterise its presentation, diagnosis, management and outcome by a retrospective case review of 30 patients (14 females) followed at a single tertiary paediatric endocrinology centre over a 30-year period. At presentation, median age was 8.9 years (0.2–15.5) and the commonest manifestations were weight gain (23/30), hirsutism (17/30), acne (15/30) and hypertension (15/30). Growth retardation was present in 11/30. Median body mass index (BMI) was +2.1 standard deviation score (SDS) (−6.5 to +4.6). Urinary free cortisol (UFC) was abnormal in 17/18 (94 %), midnight cortisol in 27/27 (100 %) and low-dose dexamethasone suppression (LDDS) test in 20/20 (100 %). High-dose dexamethasone suppression (HDDS) test was abnormal in 6/6 (100 %) of adrenal tumours, 1/10 (10 %) of Cushing disease (CD) and 1/2 (50 %) of ectopic tumours. Bilateral inferior petrosal sinus sampling (IPSS) identified five CD cases and one ectopic tumour. All patients underwent surgery and subsequently required cortisol replacement. Final diagnoses were 16 CD, 11 adrenal disease, 2 ectopic ACTH-secreting lesions and 1 case of unidentified aetiology. One year post-diagnosis, median BMI was 0.5 SDS (−2.5 to +3.7), hypertension was present in 4/14 (28 %), and 43 % (12/30) of individuals were off hydrocortisone.