Summary: A vegan diet is increasingly popular. It consists of consuming only plant based products while eliminating all animal ones, including eggs, dairy and honey. Increasing number of plant-based products in the diet is associated with numerous health benefits and can be used in the prevention and treat-ment of most non-communicable diseases, such as obesity, type 2 diabetes, hypertension, atherosclerosis or selected neoplasms. Despite many benefits, a vegan diet, especially improperly composed, may increase the risk of nutritional deficiencies. The most common problems include vitamin B12 deficiency and low consumption of omega-3 fatty acids, as well as vitamin D deficiencies. The aim of this article is to identify the most common deficiencies among people following a vegan diet based on current scientific research.