Background: It is unclear whether functional outcomes improve or deteriorate with age following surgery for Hirschsprung's disease. The aim of this cross-sectional study was to determine the long-term functional outcomes and quality of life (QoL) in patients with Hirschsprung's disease. Methods: Patients with pathologically proven Hirschsprung's disease older than 7 years were included. Patients with a permanent stoma or intellectual disability were excluded. Functional outcomes were assessed according to the Rome IV criteria using the Defaecation and Faecal Continence questionnaire. QoL was assessed by means of the Child Health Questionnaire Child Form 87 or World Health Organization Quality of Life questionnaire 100. Reference data from healthy controls were available for comparison. Results: Of 619 patients invited, 346 (55·9 per cent) responded, with a median age of 18 (range 8–45) years. The prevalence of constipation was comparable in paediatric and adult patients (both 22·0 per cent), and in patients and controls. Compared with controls, adults with Hirschsprung's disease significantly more often experienced straining (50·3 versus 36·1 per cent; P = 0·011) and incomplete evacuation (47·4 versus 27·2 per cent; P < 0·001). The prevalence of faecal incontinence, most commonly soiling, was lower in adults than children with Hirschsprung's disease (16·8 versus 37·6 per cent; P < 0·001), but remained higher than in controls (16·8 versus 6·1 per cent; P = 0·003). Patients with poor functional outcomes scored significantly lower in several QoL domains. Conclusion: This study has shown that functional outcomes are better in adults than children, but symptoms of constipation and soiling persist in a substantial group of adults with Hirschsprung's disease. The persistence of defaecation problems is an indication that continuous care is necessary in this specific group of patients.