Aetiology of inflammatory bowel disease (IBD) is complex and probably multifactorial. Nutrition has been proposed to be an important aetiological factor for development of IBD. Several components of the diet (such as sugar, fat, fibre, fruit and vegetable, protein, fast food, preservatives etc.) were examined as possible causative agents for IBD. According to some researchers infant feeding (breast feeding) may also contribute to the development of IBD. Though the importance of environmental factors is evidenced by the increasing incidence in developed countries and in migrant population in recent decades, the aetiology of IBD remained unclear. There are many theories, but as yet no dietary approaches have been proved to reduce the risk of developing IBD. The role of nutrition in the management of IBD is better understood. The prevention and correction of malnutrition, the provision of macro- and micronutrients and vitamins and the promotion of optimal growth and development of children are key points of nutritional therapy. In active disease, the effective support of energy and nutrients is a very important part of the therapy. Natural and artificial nutrition or the combination of two can be chosen for supporting therapy of IBD. The author summarises the aetiological and therapeutic role of nutrition in IBD.