Paratuberculosis is a chronic inflammatory bowel disease in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Paratuberculosis is one of the most economically damaging diseases of ruminants; it's control is essential for economic production. Due to the long incubation period of the disease (2-10 years), less than 5% of cases develop characteristic clinical symptoms. Eradication of paratuberculosis is challenging due to the long incubation period, late onset of clinical signs, and low-sensitivity diagnostic tests due to specific disease progression and immune response. The authors present the diagnostic methods of paratuberculosis in details, discussing their pros and cons. Bacterium detection in faeces and antibody testing in serum or milk are the most commonly used diagnostic methods for detecting the disease. With the quick and cost-effective ELISA method, the MAP occurrence can be detected in the herd, but false-negative results may show up. The bacterial detection is the best method to find the animals in the early stage of the disease, but intermittent shedding should be taken into account. The bacterial culture is also a good method to estimate the rate of shedding. The authors' opinion is that a combination of different diagnostic tests can be the basis for the eradication programs.