Mycobacterium avium subsp. paratuberculosis (MAP) is the cause of paratuberculosis mainly in domestic and wild ruminants; paratuberculosis is also known as Johne’s disease. This disease is endemic all over the world generating significant economic losses, especially in dairy herds, although, MAP is the cause of infection in many other species including primates. Currently, MAP mycobacteria are recognized as pathogens transmitted by food. They are a potential threat to animal and human health. Infected animals excreting mycobacteria with faeces are the main source of MAP. The development of control strategies and disease control are based on determi- nation of the genetic diversity of the MAP strains causing Johne’s disease. This study describes 43 strains isolated from a herd of dairy cows located in northern Poland. The types of MAP were determinted based on the polymorphism analysis of two insertion fragments: IS900 and IS1311. The polymorphism of IS900 was analyzed with the use of a PCR multiplex according to Collins’ method and the IS1311 polymorphism with the use of the PCR-REA method. Based on the diffe- rences observed, the strains isolated were classified into two MAP types, cattle (C-type) and sheep (S-type), with the predominance of the cattle type.