Current data indicate a change in the epidemiology of inflammatory bowel diseases. The disease has become more widespread and the rise in the incidence has been reported in all age groups including early childhood and according to recent data also the elderly population. Some earlier studies have suggested that the phenotype and natural history of the disease may be different according to age of onset. Recently the importance of age at onset was reported in two population-based studies from France and Hungary including both paediatric and adult onset inception cohorts. Early onset disease was associated with more frequent disease extension in both Crohn’s disease and ulcerative colitis and in most but not all studies with higher frequency of complicated disease behaviour. This is also accompanied by striking differences in the medical management with earlier and more prevalent (2–3-fold) use of immunosuppressives and to some extent biologicals in patients with early compared to elderly-onset disease, especially in Crohn’s disease. However, the results of population-based studies on impact of age on surgery rates in Crohn′s disease as well as ulcerative colitis are conflicting. Furthermore, published data indicate that relative but not absolute risk of developing cancer and mortality is higher in patients with an early onset disease. Critical reviews that focus on the importance of age at onset in inflammatory bowel disease are rare. Therefore, the aim of this review is to describe the differences in epidemiology, clinical characteristics, and natural history of paediatric and elderly-onset inflammatory bowel disease based on studies performed in general population.