The article presents some facts about vegetarian diet, its influence on child development, possible complications and their prevention. A vegetarian diet, if properly selected, can meet all the requirements of the growing child. A strictly vegetarian (vegan) diet can cause vitamin B12 deficiency with serious neurological and haematological disturbances. To prevent vitamin B12 deficiency we should recommend the inclusion of algae (Chlorella, Spirulina) in vegan diet. These algae are the most important non-animal source of vitamin B12.