An accurate differential diagnosis of the type of diabetes mellitus (DM) is one of the important conditions for a personalized choice of adequate therapy in modern diabetology. In this regard, particular attention is paid to the secondary diabetes due to a whole group of heterogeneous exocrine pancreatic diseases resulting from different pathogenesis, which are combined for classification purposes with chronic pancreatitis (CP) taking the leading role. The literature review presents an integral view of the problem based on an analysis of modern diabetological and gastroenterological guidelines. It discloses terminological transformation of this diabetes into type 3c diabetes and discusses the problem of assessing prevalence of type 3c diabetes. Clinical features are considered in close connection with pathogenetic, which makes it possible to represent type 3c DM as a special morphofunctional disorder with an emphasis on high risk of ductal adenocarcinoma of the pancreatic gland. The complexity of its verification is discussed in close connection with the diagnosis of СP. The article describes the approaches to the therapy of type 3c diabetes depending on its specific cause and emphasises the special significance of correction of exocrine pancreatic deficiency. It substantiates the variety of clinical subtypes of type 3c diabetes with different degrees of carbohydrate metabolism disorders, which suggests the use of various hypoglycemic therapy regimens. In the absence of specific algorithms, it discusses the principles of monitoring hyperglycaemia compared with those for type 1 and 2 diabetes: possibilities and limitations of non-insulin hypoglycemic drugs and the principles of insulin therapy.